What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

User Agent Wikipedia

Ellen Grant
• Thursday, 08 October, 2020
• 54 min read

During the first browser war, many web servers were configured to send web pages that required advanced features, including frames, to clients that were identified as some version of Mozilla only. Other browsers were considered to be older products such as Mosaic, Cello, or Samba, and would be sent a bare-bones HTML document.

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Automated agents are expected to follow rules in a special file called robots.txt “. The popularity of various Web browser products has varied throughout the Web's history, and this has influenced the design of websites in such a way that websites are sometimes designed to work well only with particular browsers, rather than according to uniform standards by the World Wide Web Consortium (W3C) or the Internet Engineering Task Force (IETF).

Websites often include code to detect browser version to adjust the page design sent according to the user agent string received. Thus, various browsers have a feature to cloak or spoof their identification to force certain server-side content.

For example, the Android browser identifies itself as Safari (among other things) in order to aid compatibility. User agent sniffing is the practice of websites showing different or adjusted content when viewed with certain user agents.

An example of this is Microsoft Exchange Server 2003's Outlook Web Access feature. When viewed with Internet Explorer 6 or newer, more functionality is displayed compared to the same page in any other browsers.

Web browsers created in the United States, such as Netscape Navigator and Internet Explorer, previously used the letters U, I, and N to specify the encryption strength in the user agent string. Until 1996, when the United States government disallowed encryption with keys longer than 40 bits to be exported, vendors shipped various browser versions with different encryption strengths.

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^ a b RFC 3261, SIP: Session Initiation Protocol, IETF, The Internet Society (2002) ^ RFC 7231, Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, IETF, The Internet Society (June 2014) ^ Net news Article Format. Browser Versions Carry 10.5 Bits of Identifying Information on Average “, Electronic Frontier Foundation, 27 January 2010.

I've been rejected until I come back with Netscape” ^ “Android Browser Reports Itself as Apple Safari”. ^ User Agent String explained: Android WebKit Browser”.

Mozilla/5.0 (Linux; U; Android 2.2; ends; HTC_DesireHD_A9191 Build/FRF91) Apple WebKit/533.1 (HTML, like Gecko) Version/4.0 Mobile Safari/533.1 ^ Emberton, Stephen. ^ “Chrome Phasing out Support for User Agent ".

During the first browser war, many web servers were configured to only send web pages that required advanced features, including frames, to clients that were identified as some version of Mozilla. Other browsers were considered to be older products such as Mosaic, Cello, or Samba, and would be sent a bare-bones HTML document.

Automated web crawling tools can use a simplified form, where an important field is contact information in case of problems. By convention the word “bot” is included in the name of the agent .

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Automated agents are expected to follow rules in a special file called robots.txt “. The popularity of various Web browser products has varied throughout the Web's history, and this has influenced the design of websites in such a way that websites are sometimes designed to work well only with particular browsers, rather than according to uniform standards by the World Wide Web Consortium (W3C) or the Internet Engineering Task Force (IETF).

Websites often include code to detect browser version to adjust the page design sent according to the user agent string received. Thus, various browsers have a feature to cloak or spoof their identification to force certain server-side content.

For example, the Android browser identifies itself as Safari (among other things) in order to aid compatibility. On the Internet, this will result in a different site being shown when browsing the page with a specific browser.

One example of this is Microsoft Exchange Server 2003's Outlook Web Access feature. When viewed with Internet Explorer 6 or newer, more functionality is displayed compared to the same page in any other browsers.

Portals, often rely heavily on user agent sniffing, since mobile browsers often differ greatly from each other. These differences can be small, e.g., resizing of certain images to fit smaller screens, or quite extensive, e.g., rendering of the page in WML instead of XHTML.

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Web browsers created in the United States, such as Netscape Navigator and Internet Explorer, previously used the letters U, I, and N to specify the encryption strength in the user agent string. Until 1996, when the United States government disallowed encryption with keys longer than 40 bits to be exported, vendors shipped various browser versions with different encryption strengths.

Following the lifting of export restrictions, most vendors supported 256-bit encryption. ^ a b RFC 3261, SIP: Session Initiation Protocol, IETF, The Internet Society (2002) ^ RFC 7231, Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, IETF, The Internet Society (June 2014) ^ Net news Article Format.

Browser Versions Carry 10.5 Bits of Identifying Information on Average “, Electronic Frontier Foundation, 27 January 2010. I've been rejected until I come back with Netscape” ^ “Android Browser Reports Itself as Apple Safari”.

^ User Agent String explained: Android WebKit Browser”. Mozilla/5.0 (Linux; U; Android 2.2; ends; HTC_DesireHD_A9191 Build/FRF91) Apple WebKit/533.1 (HTML, like Gecko) Version/4.0 Mobile Safari/533.1 ^ Emberton, Stephen.

Walker soon developed a following of his own, with Grunewald admitting that his best-selling cover of the comic was #321 which had an image of Captain America shooting a firearm, and that this resulted in many fans wanted him to “Symbolize” Cap and make him more Punished or Wolverine-like. Grunewald considered this a violation of the characters principles, so decided that he would give the fans what they wanted but that it couldn't be Steve Rogers.


Agent (created by writer Mark Grunewald and artist Keaton Dwyer) using a discarded costume of Steve Rogers (the original Captain America): a black outfit with a different alignment of the Stars and Stripes to differentiate it from Steve Rogers' suit. He continued to use that uniform in his 2001 miniseries, which followed the events in “Maximum Security” and was written and drawn by Jerry Norway.

John Walker was born in the fictional town of Custer's Grove, Georgia. He grew up idolizing his older brother, Mike, a helicopter pilot who died in the Vietnam War in 1974.

John wanted to live up to Mike's memory, who was idolized by their parents, and so he later enlisted in the military. John served at Fort Bragg, although it was never specifically stated which unit he was attached to.

After John received an honorable discharge from the United States Army, he was told by a friend about the Power Broker, a mysterious individual who gave people superhuman abilities. Walker and his friend received treatments that granted them superhuman abilities.

Art by Mike Deck and Bob McLeod. Walker, now in debt to the Power Broker, intends to join the Unlimited Class Wrestling Federation but meets Ethan Therm who becomes his manager and persuades Walker to become a hero instead. Therm secures financial backing, helps Walker design a costume, and sets out a strategy that allows him to debut as the corporate-sponsored Super-Patriot, who then travels the country promoting his image to the nation through patriotic rallies and community service.

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At a rally in Central Park, he holds a secretly rehearsed performance in which he publicly criticizes Captain America and is subsequently attacked by three extremist supporters of Captain America called the Bold Urban Commandos or “Buckles”. Walker defeats them in the staged fight as a demonstration of his combat prowess and patriotism.

Captain America confronts Walker privately afterwards and demands that he stop using the Buckles, since people attending the rally could have been hurt in a panic resulting from the staged attack. Walker refuses, arguing that his actions are justified by his quest to replace the outdated Captain America as the nation's symbol.

With neither man falling after a lengthy brawl, Super-Patriot flings a number of throwing stars at Captain America. A weary and dejected Captain America tries to tell himself that the fight was a draw, as neither man actually went down.

But he is nonetheless left questioning his own fighting abilities while acknowledging Super-Patriot's superior strength and stamina. Walker scales the monument, disarming him with a throwing star, before sending him plummeting to the ground below.

The Commission debate who should become the new Captain America, with Nick Fury and Sam Wilson (the Falcon) both being considered as candidates, although it was considered that the former was too old and would not want to give up the autonomy he enjoyed as Director of S.H.I.E.L.D, whereas in the case of the latter they did not believe that the United States was ready for a black Captain America. Dr. Valerie Cooper, a member of the Commission, suggests that Walker should be made the new Captain America, as a U.S. government operative.

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Though repulsed by the notion of giving up being Super-Patriot and taking on the identity he has criticized so much, Walker ultimately answers, “Ma'am, if Uncle Sam wanted me to be Mickey Mouse, I'd do it.” In becoming Captain America, he is forced to abandon Thrum as his manager, and can only retain one of the “Buckles”, Lamar Hopkins, since the other two fail to pass background checks.

Another of Walker's early acts as Captain America was a mission to “aid stability and democracy in South America” by teaming up with the Tarantula in order to hunt escaped political dissidents from his home country on behalf of its oppressive regime in order to silence them. Despite believing in the fight against Communism and in the principle of helping America's “Democratic allies in Latin America”, Walker becomes increasingly uncomfortable with the methods used by Tarantula after he interrogates and threatens occupants of an immigration detention center for information on his targets.

His superhuman strength and lack of emotional control lead him to inadvertently beat Professor Power to death. The two rejected “Buckles”, now calling themselves Left-Winger and Right-Winger, crash the press conference arranged by Cooper to reveal the “new” Captain America and Battle star, and announce Walker's name and birthplace on national TV.

His parents are subsequently killed by The Watchdogs; this incident drives Walker closer to a mental breakdown, particularly when the Commission orders him not to step out of line in the future, resulting in him missing his parents' funeral due to his new responsibilities. In a state of rage, he kills many of the Watchdogs, and beats Left-Winger and Right-Winger to a pulp, leaving them to die in an explosion.

Walker is then captured by Flag-Smasher, but rescued by the original Captain America, Battle star, and D-Man. The Red Skull, now in a clone body of Steve Rogers, lures Walker to Washington, D.C.

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To address Walker's psychosis, he is hypnotized into believing his parents are still alive, and he would not recover his full memory for many years. He is also given a new cover identity of 'Jack Daniels' as well as speech therapy and work to erase old mannerisms in order to help hide the fact that he was the man the public had recently seen “assassinated”.

Agent, wearing a variation of the costume that Rogers had worn as the Captain and using his uranium disc as a shield. He was placed as a watchdog of West Coast Avengers and the Vision by the Commission, as a condition to possibly get their government clearance reinstated.

Some time later, he rescued Battle star from the Power Broker, and reconciled with him; Walker learned that his memories had been altered and that his parents were dead. The manner of his appointment to the West Coast Avengers team, and his own abrasive attitude, saw U.S.

Agent takes down the superpowered mercenary Paladin, who had been employed to kill the Punished by the Maggie, breaking both of his legs with his shield. Agent by dressing a deceased henchman in his uniform and leaving him in a burning building, convincing U.S.

Agent is berated by his employers who inform him that his job is to act, not think and declaring that it is no wonder that he failed as Captain America. Agent was once more forced to choose between following the rules and laws of the nation he had dedicated himself to serving, or ignoring them in favor of doing what he personally believed to be right, when he investigated a series of gruesome murders of illegal immigrants on the Mexico/U.S. border who he later discovered were being committed by a corrupt law enforcement official.


Thomas Holloway is subsequently arrested for his crimes and the Scourge program seemingly closed down. Even with his personality conflicts and reckless behavior, he soon proved himself worthy of being an Avenger and was able to rejoin.

Agent's fury who raised his hand to strike Captain America; Iron Man stopped him and uttered, “Not now. Soon after, most of the then-current members of the West Coast Avengers were asked by Tony Stark to found Force Works.

Agent ultimately joined the new team, wearing a new costume and using an energy-based shield provided to him by Tony Stark. Agent as a “loose cannon”, suggesting that he could have an identity problem, expressing the desire to develop a new look for him “to get U.S.

Agent travels to an isolated region of Tennessee in order to locate Hawkeye (Clint Barton) who had disappeared after the death of his then-wife Mockingbird. Angry at the fact that Hawkeye had abandoned his teammates when they had desperately needed his support to avoid the dissolution of the West Coast Avengers, U.S.

Agent briefly appears in Captain America (Vol 3) during the 'American Nightmare' story arc attempting to steal an experimental jet plane. He eventually became the field leader of the Jury, a group of armored corporate vigilantes, owned by Edwin Cord, owner of Cord co.

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Following his recovery, he soon adopted a new costume and rejoined the Commission on Superhuman Activities, with the position at the head of the federal government's U.S. Marshal division, called S.T.A.R.S., the Superhuman Tactical Activities Response Squad.

The group battled alien invaders and superhuman threats and was responsible for their imprisonment. Agent continued to work for S.T.A.R.S as America's super human 'top cop' under the observation of Valerie Cooper.

Agent and Tries teamed up to tackle a radical faction of Atlantis working with the super-villain Pound cakes (Marian Pounce). It transpired that Pounce was attempting to trade more of the alien parasites capable of mind control with the Atlantis.

At this point Captain America (Steve Rogers), who had been revealed to be the S.H.I.E.L.D envoy responsible for collecting the parasites, along with Kali Tries, burst into the meeting between U.S. Power Broker places a parasite on the neck of Senator Swarovski intent upon influencing his address to the International assemblage of Heads of State, but is interrupted by U.S.

Meanwhile, Tries is captured by the Power Broker who reveals that he had been attacked and left for dead by aliens during the 'Maximum Security' crisis at which point, barely alive, he had become the host for an alien which produced the mind-controlling parasites, subsequently attempting to expand its control by infecting influential individuals. Eventually Agent manages to escape Captain Americas attentions long enough to reveal the presence of the parasite on Senator Swarovski's neck and removes it with his energy baton.


Agent that Tries, far from being a traitor, was actually a deep cover agent acting on behalf of S.H.I.E.L.D with the intention of gaining Senator Swarovski's confidence and discovering who was using the parasites and attempting to take the mother-parasite into custody for study and as evidence. Agent destroys the specimen and then speculates that he didn't believe it to be alien at all but rather a product of a government genetics lab that went wrong.

Rogers retorts that Captain America represents an ideal for all people, of all countries. Mazikandar's dictator is presented to his hand-picked successor, who promptly executes his predecessor on the steps of the capitol building to the surprise of both the Invaders and Avengers alike.

The murder of a man without trial causes a further schism with the Avengers, who blame the New Invaders for declaring open war on Mazikhandar. Enamor responds that Mazikhandar had declared war on his nation when they decided to pollute the oceans.

Captain America (Steve Rogers), while attempting to close down the New Invaders, threatened Walker with legal action over his use of the uniform, stating that he owned the copyright to it. Walker saved Enamor from a brainwashed and murderous Wolverine, who had been resurrected by The Hand during the “Enemy of the State” storyline.

Agent's defeat gives Tony Stark the leverage to finally persuade him to join Omega Flight when he reveals that the Purple Man has fled north himself. During a mission to take down unregistered super-criminal Entails, Weapon Omega passes out mid-combat for unknown reasons forcing U.S.


It later transpires that Weapon Omega is being manipulated by Omega Flight's handler Agent Brown as well as his psychologist Dr. Benning, but worse than that unregistered super-criminals are being detained, with no record being made of their detention, and their powers are being used to fuel Weapon Omega's energy absorbing power, resulting in the deaths of several of the inmates who are completely drained of life. Agent is acting on behalf of Tony Stark (Iron Man) who is monitoring Weapon Omega's progress and requires U.S.

Agent in order to uncover the conspiracy, spies and informs him that Weapon Omega isn't resting and for some reason he is being constantly observed. This results in Omega losing control as he manifests the various powers of numerous inmates, breaking U.S.

Dr. Benning boasts that as a fail-safe had been activated, all evidence of her manipulation of Weapon Omega had been destroyed. It is at this point that Omega reveals that one of the individuals whose powers he had absorbed had been a techno path, and that he had accessed all of Benning's confidential records and sent them to Tony Stark.

Agent is removed from Omega Flight by Loki (disguised as the Scarlet Witch) to aid Hank Pym in defeating the reality-altering Cotton. Agent finds himself in combat with the anti-registration Hulk and Hercules, but they later endeavor to team up against their common foe.

Agent plays a part in separating him from that source by planting explosives in order to destroy it. The team is sent on various missions including saving the Infinite Avengers Mansion from becoming untethered from reality.

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He attacks the current Captain America, James “Bucky” Barnes while in this condition. He said he believes that the Gods are just people with superpowers and battled against Eris, Goddess of discord.

Following a conflict involving a Cosmic Cube-empowered Absorbing Man and the Dark Avengers, U.S. Agent and several members of the now disbanded Mighty Avengers are called upon by Amadeus CHO during the events of Siege.

Their mission is to stop Norman Osborn's Thunderbolts from stealing Odin's spear from the Agrarian armory. As thanks for his service during the siege of Asgard, John Walker is appointed the new warden of The Raft maximum security prison.

The injuries he sustained during his fight with Nuke have left him wheelchair bound and using a prosthetic arm. He refuses to repair his body using more technologically advanced prostheses because he does not want to become a cyborg like the man who crippled him.

Walker engaged several inmates in hand-to-hand combat during a prison riot, demonstrating that he could still hold his own despite some limitations. During the Fear Itself storyline, Juggernaut heavily damaged the Raft before escaping, causing a prison break.


This triggered a security fail-safe in one section of the jail which reversed the air supply, eventually creating a fatal vacuum. He was assisted by Ghost, who earned Walker's respect after protecting the lives of the ungrateful inmates.

Walker also rallies other help, inmate and powered alike, to assist him in his duties throughout this crisis. Agent's traditional red, white and black shield followed by the tag line 'EVIL is our only HOPE!'.

June Covington is seemingly able to restore his lost limbs with help from this reality's version of the Venom symbiote in lobotomized form. At first John declines the request, out of respect for Steve's decision to share the mantle with Sam, until they see a news report about Sam and former New Warrior Rage fighting the AmeriCorps, a private police force funded by Keane Industries.

Sam refuses, acknowledging his mistakes when he assumed the mantle, and the two begin to fight, with John gaining the upper hand due to his powers. Agent was then reported missing in action on a secret mission to Syria, with a possible implication that his disappearance may have been the result of the now evil Steve Rogers' machinations.

Agent appears briefly alongside the American resistance forces, including fellow former West Coast Avengers teammates Mockingbird and Tiara. Together while aiding other allied group of superhero and super-villain resistances, they battle the Superior Octopus (Otto Octaves) and the forces of Steve Rogers' Hydra organization which took over America.

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Sam Wilson/All-New Captain America, Ant-Man (Scott Lang) and Winter Soldier manage to redeem Robin and return the real Steve Rogers back from his imprisonment inside the Cosmic Cube, allowing the real Steve (who immediately dons his classic Captain America costume) to defeat his Hydra counterpart. He later joined a team of heroes recruited by Captain Marvel to hunt down the Punished for his actions when he was a member of Hydra Supreme Steve Rogers's “Secret Empire”, even though the Punished had been manipulated by Hydra, and was now hunting every last one of them in revenge.

Agent, believing that the Steve Rogers who had lead Hydra had been the genuine article, later confronted the real Rogers as he investigated a new spate of murders by the vigilante the Scourge of the Underworld, beating him and accusing him of manipulating him. He is stopped when Misty Knight activates a stasis beam to hold him in place, at which point Rogers explains that he did not commit the crimes U.S.

Agent forms part of a new iteration of the superhero team Force Works during the “Iron Man 2020” storyline. Assembled to act as the U.S. governments last, the best line of defense against an uprising of robots and artificial intelligences, they are sent to the fictional South American nation of Lingers where their aircraft is shot down by local rebels.

Agent is forced to fight off a group of rebels with the assistance of Mockingbird before rendezvousing with the rest of the team, at which point they are attacked and seemingly overwhelmed by a group of rebels infected with Decathlon technology. While held captive with his shield confiscated, it is revealed that the Deathless want the team for spare parts in their war against an even bigger threat, that of Ultimo.

Though Lingers doesn't have enough radioactive signatures for them to harness, they will make use of the War Machine's arc reactor as MOD OK Superior tells Quake to call Ultimo. Once War Machine gets a clear shot on the head, MOD OK Superior reveals his true motives: to connect to Ultimo's headless body to become Ulti-MODOK.

War Machine's plan involves using a generator in the bunker to jump start his armor's arc reactor. Once his arc reactor has been re-energized, James Rhodes has Quaked distract Ulti-MODOK in the War Machine armor to buy the rest of Force Works time to figure out how to stop the Deathless.

Ulti-MODOK falls into the lava in the chasm that Quake opened as the Deathless follow him in, attacking to get him in there. A day later at a secure medical facility, Maria Hill reprimands War Machine, U.S.

After finishing the lecture by stating she has sent out a scrub team with flamethrowers and EMP guns to destroy the evidence of what happened on Lingers, she fires them from Force Works and takes the flash drive with MOD OK's Decathlon plans from U.S. The rest of the group is against Maria obtaining the Decathlon plans, until Mockingbird deduces U.S.

As a result of the experimental mutagenic augmentation process conducted on him by Dr. Karl Males on behalf of the Power Broker, John Walker has superhuman strength (capable of lifting ten tons under maximum exertion), agility, reflexes/reactions, and endurance. His speed, dexterity, coordination, and balance are of the order of a superior Olympic athlete.

Agent is an exceptional hand-to-hand combatant and highly trained in gymnastics and acrobatics, having received rigorous training in unarmed combat and the use of his shield in a style similar to Captain America's own fighting style by the Taskmaster. He is a seasoned combat veteran with military combat experience in tactical and strategic planning, observations, and special operations, has been shown to have a fluent grasp of the Arabic language, and Spanish, is technically proficient enough to bypass an advanced security system, is a qualified fixed-wing pilot, a trained scuba diver, and is highly proficient in the use of conventional firearms.

He has great accuracy at throwing his shield and due to his superhuman strength, it is potentially a lethal weapon. Agent has used a variety of shields in his time, initially inheriting Captain America's indestructible circular shield after Steve Rogers had relinquished it upon quitting the role and refusing to work for the Commission for Super Human Activities.

Agent then briefly adopted a remote control shield against Hawkeye and the Thunderbolts. The shield was decorated with the names of Americans who had died at the hands of terrorists as well as a photograph of U.S.

That allowed him to continue to walk, and according to then-Director Sharon Carter may have also provided “An additional benefit or two”. Agent's costume incorporated a “thought relay receptor” that picks up his mental commands and shapes his shield however he wills it.

In his first costumed identity as the Super Patriot, Walker wore a costume that was capable of stopping multiple shots from a handgun at point-blank range, and also used throwing stars and a flame torch. In an alternate reality John Walker becomes Captain America and battles with Steve Rogers, with only the intervention of Nick Fury and then-President Ronald Reagan bringing the hostilities to an end.

In another dystopian alternate reality in which Captain America's (Steve Rogers) icy tomb was not discovered by the Avengers until much later in history, U.S. He questions why Magneto is present, to which Nick Fury answers “anyone who is not a zombie is an ally”.

SS Agent has a costume and photonic energy shield similar to that worn and used by USA gent during his time with Force Works. He fought against the Communists during the Cold War, although he was dangerously out of control because of his use of dark magic and was placed into suspended animation by the military.

In 1995, Tobit released an action figure line for the 1994 Iron Man animated series. However, the figure eventually did get released in international markets and the odd short packed case.

The figure was later remolded to become the Astral Armor Professor Xavier in the X-Men toy line. Agent wearing the original costume into Wave 3 of their Return of Marvel Legends line.

^ Interview with Mark Grunewald in Amazing Heroes #146 (1988) ^ “Marvel's USA gent Reports for Duty in New Miniseries Debuting This Fall”. 1 (July 2007) ^ Ultimate Comics: X-Men #8–9 ^ A-Next #10–11 ^ Secret Warps: Soldier Supreme Annual #1 ^ Couch, Aaron (August 23, 2019).

If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks. Computing Wikipedia :WikiProject ComputingTemplate:WikiProject ComputingComputing articles C This article has been rated as C-Class on the project's quality scale. The sentence “Spam bots and Web scrapers often use fake user agents.

For example, the Android browser identifies itself as Safari in order to aid compatibility.” The phrase should be changed or moved to make it more clear to the reader, and to eliminate any unintended implications.

In case anyone is wondering, I got the IE7.0b UA from this MSN blog Aidan 08:14, Apr 28, 2005 (UTC) -- rob 05:17, 18 September 2005 (UTC) Most statistics software are able to recognize Opera and count it as such.

I was extremely disappointed to come here today and find that great resource (the most excellent list of strings) GONE. -- angry keyboarder (a/k/a:Scott) 00:55, 19 May 2007 (UTC)They are incredibly useful for testing web links, though.

An user agent and an user agent string are generally used interchangeably... -- Eraserhead1 < talk > 21:56, 19 January 2010 (UTC)That is clearly sloppy usage, a UA is foremost the application or software component, the article now properly delineates the identification as well. -- Eraserhead1 < talk > 22:03, 19 January 2010 (UTC) It seems that the majority of this article is about User agent identification in computer protocols.

-- Guy Macon (talk) 18:54, 28 November 2013 (UTC) I have long thought that whilst a website may need to know what browser is in use for the sake of page layout issues, there is little justification for disclosing what OS the browser is running on. Doing so increases the risk of a compromised website being able to take control of the visitor's computer by way of a known vulnerability.

The end of support for Windows XP has highlighted this issue, though it's one which has existed for many years. Basically, the Internet is a hostile environment, and the less you tell a potential crook about you, either by UA or scripting, the better.

-- Guy Macon (talk) 19:44, 10 April 2014 (UTC)Yes there are several ways to stop the OS being reported. However, the more pertinent question is whether it should be reported without the user's permission, after all it could be seen as an unwarranted disclosure of private data.

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Source check}}). , “External links modified” talk page sections are no longer generated or monitored by InternetArchiveBot.

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Anotherbigal (talk) 12:16, 10 June 2016 (UTC)== Make it clearer for non-technical user == I presume to someone with technical knowledge this article make a lot of sense.

The user agent transmits information such as the browser version, installed plug-ins, and other data to the web server. The information that identifies the user agent is transferred to the web server in the HTTP request header.

In the early days of the internet, Microsoft's first Internet Explorer pretended to be a Netscape browser to access web pages designed for Netscape Navigator, the dominant browser on the market back then. Browsers like Mozilla Firefox, Google’s Chrome as well as Safari and Opera are examples of user agents.

Slurp, MSN bot Game consoles: PlayStation, Wii, PlayStation Portable and Bungalow (the browser on the Nintendo DS) Legacy operating systems: Amiga Voyager Link checkers: e.g. W3C-Checklink SEO tools / on-page crawlers: e.g. SeobilityBot Web applications: Flash Player, Adobe Acrobat Reader, feed readers, screen readers, validators, media players, streaming portals Search engine crawlers are an example of user agents that visit websites automatically.

Once an user agent has identified itself to the web server, a process called content negotiation begins. Content negotiation is a mechanism defined in HTTP that allows you to provide different versions of a document or another resource using the same URL.

Browsers can specify which version best suits their capabilities with the help of user agent information and request the fitting resource for their needs. A classic application of this mechanism is providing an image in GIF as well as PNG format, and delivering the GIF version to user agents that cannot display PNG images (such as older versions of MS Internet Explorer).

Similarly, different stylesheets (CSS), JavaScript, or the mobile version of a web page can be rendered based on browser capabilities. When an application receives content tailored to its user agent, this process is referred to as agent name delivery.

When this black hat SEO tactic referred to as cloaking is used, visitors see a web page optimized for humans whereas crawlers access content and structure that is mostly simple and optimized for high rankings in search results. A web application which provides message management, composition, and reception functions may act as a web email client, and a piece of computer hardware or software whose primary or most visible role is to work as an email client may also use the term.

The common arrangement is for an email user (the client) to make an arrangement with a remote Mail Transfer Agent (MTA) server for the receipt and storage of the client's emails. The MTA, using a suitable mail delivery agent (MDA), adds email messages to a client's storage as they arrive.

The default setting on many Unix systems is for the mail server to store formatted messages in box, within the user's home directory. Of course, users of the system can log-in and run a mail client on the same computer that hosts their mailboxes; in which case, the server is not actually remote, other than in a generic sense.

The Post Office Protocol (POP) allows the user to download messages one at a time and only deletes them from the server after they have been successfully saved on local storage. However, there is no provision for flagging a specific message as seen, answered, or forwarded, thus POP is not convenient for users who access the same mail from different machines.

IMAP provides folders and sub-folders, which can be shared among different users with possibly different access rights. IMAP features an idle extension for real-time updates, providing faster notification than polling, where long-lasting connections are feasible.

In addition, the mailbox storage can be accessed directly by programs running on the server or via shared disks. Direct access can be more efficient but is less portable as it depends on the mailbox format; it is used by some email clients, including some webmail applications.

The email clients will perform formatting according to RFC 5322 for headers and body, and MIME for non-textual content and attachments. Headers include the destination fields, To, Cc (short for Carbon copy), and BCC (Blind carbon copy), and the originator fields From which is the message's author(s), Sender in case there are more authors, and Reply-To in case responses should be addressed to a different mailbox.

To better assist the user with destination fields, many clients maintain one or more address books and/or are able to connect to an LDAP directory server. The email client is usually set up automatically to connect to the user's mail server, which is typically either an MSA or an MTA, two variations of the SMTP protocol.

Client settings require the name or IP address of the preferred outgoing mail server, the port number (25 for MTA, 587 for MSA), and the username and password for the authentication, if any. There is a non-standard port 465 for SSL encrypted SMTP sessions, that many clients and servers support for backward compatibility.

With no encryption, much like for postcards, email activity is plainly visible by any occasional eavesdropper. Without it, anyone with network access and the right tools can monitor email and obtain login passwords.

Examples of concern include the government censorship and surveillance and fellow wireless network users such as at an Internet café. All relevant email protocols have an option to encrypt the whole session, to prevent a user's name and password from being sniffed.

They are strongly suggested for nomadic users and whenever the Internet access provider is not trusted. S/MIME employs a model based on a trusted certificate authority (CA) that signs users' public keys.

Open PGP employs a somewhat more flexible web of trust mechanism that allows users to sign one another's public keys. Header fields, including originator, recipients, and subject, remain in plain text.

In addition to email clients running on a desktop computer, there are those hosted remotely, either as part of a remote UNIX installation accessible by telnet (i.e. a shell account), or hosted on the Web. Both of these approaches have several advantages: they share an ability to send and receive email away from the user's normal base using a web browser or telnet client, thus eliminating the need to install a dedicated email client on the user's device.

The main limitations of webmail are that user interactions are subject to the website's operating system and the general inability to download email messages and compose or work on the messages offline, although there are software packages that can integrate parts of the webmail functionality into the OS (e.g. creating messages directly from third party applications via MAPI). Like IMAP and MAPI, webmail provides for email messages to remain on the mail server.

By contrast, both IMAP and webmail keep messages on the server as their method of operating, albeit users can make local copies as they like. With limited bandwidth, access to long messages can be lengthy, unless the email client caches a local copy.

There may be privacy concerns since messages that stay on the server at all times have more chances to be casually accessed by IT personnel, unless end-to-end encryption is used. Another important standard supported by most email clients is MIME, which is used to send binary file email attachments.

Email servers and clients by convention use the TCP port numbers in the following table. For MSA, IMAP and POP3, the table reports also the labels that a client can use to query the SRV records and discover both the host name and the port number of the corresponding service.

It simply provides a warning that transmitting user credentials in clear text over insecure networks SHOULD be avoided in all scenarios as this could allow attackers to listen for this traffic and steal account data. Unlike SMTP, however, it needs authentication: Users have to identify themselves and prove they're who they claim to be.

Unfortunately, the authentication usually consists of presenting a username and a password known only to the user and the POP3 server. Because SSL-wrapped POP3 sessions are encrypted from beginning to end, no messages, usernames, or passwords are exposed in clear text.

This solves the problem of the disclosure of reusable passwords, but does nothing to prevent eavesdroppers from reading users' mail messages as they're being retrieved.” ^ Updated Transport Layer Security (TLS) Server Identity Check Procedure for Email-Related Protocols.

In addition to providing remote shell access and command execution, OpenSSH can forward arbitrary TCP ports to the other end of your connection. This can be very handy for protecting email, web, or any other traffic you need to keep private (at least, all the way to the other end of the tunnel).

Ssh accomplishes local forwarding by binding to a local port, performing encryption, sending the encrypted data to the remote end of the ssh connection, then decrypting it and sending it to the remote host and port you specify. Now to encrypt all of your POP traffic, configure your mail client to connect to localhost port 110.

It will happily talk to mail host as if it were connected directly, except that the entire conversation will be encrypted. Clear text Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access.

Strong SIP, that NGC user agent he cap men CA Diem KET thus CUA MOT fief true thong. Aug 2015: This Wiki stats traffic report has been discontinued, due to lack of maintenance.

Note: page may load slower on Microsoft Internet Explorer than on other major browsers In computer science, a software agent is a computer program that acts for a user or other program in a relationship of agency, which derives from the Latin agar (to do): an agreement to act on one's behalf.

Software agents interacting with people (e.g. chatbots, human-robot interaction environments) may possess human-like qualities such as natural language understanding and speech, personality or embody humanoid form (see Asimov). Are not strictly invoked for a task, but activate themselves, may reside in wait status on a host, perceiving context, may get to run status on a host upon starting conditions, do not require interaction of user, may invoke other tasks including communication.

Nana's Category of Software Agent The term agent describes a software abstraction, an idea, or a concept, similar to OOP terms such as methods, functions, and objects. The concept of an agent provides a convenient and powerful way to describe a complex software entity that is capable of acting with a certain degree of autonomy in order to accomplish tasks on behalf of its host.

Various authors have proposed different definitions of agents, these commonly include concepts such as Persistence (code is not executed on demand but runs continuously and decides for itself when it should perform some activity) autonomy (agents have capabilities of task selection, prioritization, goal-directed behavior, decision-making without human intervention) social ability (agents are able to engage other components through some sort of communication and coordination, they may collaborate on a task) reactivity (agents perceive the context in which they operate and react to it appropriately).

Contrasting the term with related concepts may help clarify its meaning. Franklin & Grasses (1997) discuss four key notions that distinguish agents from arbitrary programs: reaction to the environment, autonomy, goal-orientation and persistence.

Agents have flexible behavior: reactive, proactive, social. Expert systems are not designed for reactive, proactive behavior.

(Russell & Nordic 2003) hard error: no target: CITEREFRussellNorvig2003 (help) Software agents may offer various benefits to their end users by automating complex or repetitive tasks. However, there are organizational and cultural impacts of this technology that need to be considered prior to implementing software agents.

In general implementing software agents to perform administrative requirements provides a substantial increase in work contentment, as administering their own work does never please the worker. The effort freed up serves for a higher degree of engagement in the substantial tasks of individual work.

Hence, software agents may provide the basics to implement self-controlled work, relieved from hierarchical controls and interference. Such conditions may be secured by application of software agents for required formal support.

The cultural effects of the implementation of software agents include trust affliction, skills erosion, privacy attrition and social detachment. Some users may not feel entirely comfortable fully delegating important tasks to software applications.

Those who start relying solely on intelligent agents may lose important skills, for example, relating to information literacy. In order to act on a user's behalf, a software agent needs to have a complete understanding of a user's profile, including his/her personal preferences.

MAS evolved from Distributed Artificial Intelligence (DAI), Distributed Problem-Solving (DPS) and Parallel AI (Pay), thus inheriting all characteristics (good and bad) from DAI and AI. John Sculley ’s 1987 Knowledge Navigator video portrayed an image of a relationship between end-users and agents.

Being an ideal first, this field experienced a series of unsuccessful top-down implementations, instead of a piece-by-piece, bottom-up approach. The range of agent types is now (from 1990) broad: WWW, search engines, etc.

Buyer agents travel around a network (e.g. the internet) retrieving information about goods and services. Buyer agents are typically optimized to allow for digital payment services used in e-commerce and traditional businesses.

And receive Goals (Missions) from higher level agents. “Data mining” is the process of looking through the data warehouse to find information that you can use to take action, such as ways to increase sales or keep customers who are considering defecting.

'Classification' is one of the most common types of data mining, which finds patterns in information and categorizes them into different classes. Data mining agents can also detect major shifts in trends or a key indicator and can detect the presence of new information and alert you to it.

For example, the agent may detect a decline in the construction industry for an economy; based on this relayed information construction companies will be able to make intelligent decisions regarding the hiring/firing of employees or the purchase/lease of equipment in order to best suit their firm. It communicates with the POP3 mail server, without users having to understand POP3 command protocols.

It even has rule sets that filter mail for the user, thus sparing them the trouble of having to do it themselves. SNMP agent In Unix-style networking servers, HTTP is an HTTP daemon that implements the Hypertext Transfer Protocol at the root of the World Wide Web Management agents used to manage telecom devices Crowd simulation for safety planning or 3D computer graphics, Wireless becoming agent is a simple process hosted single tasking entity for implementing wireless lock or electronic leash in conjunction with more complex software agents hosted e.g. on wireless receivers.

The agent uses its access methods to go out into local and remote databases to forage for content. These access methods may include setting up news stream delivery to the agent, or retrieval from bulletin boards, or using a spider to walk the Web.

Finally, the agent may decide to take an action based on the new content; for example, to notify the user that an important event has occurred. This action is verified by a security function and then given the authority of the user.

If the user confirms that the event is important by acting quickly on the notification, the agent may also employ its learning machinery to increase its weighting for this kind of event. Bots can act on behalf of their creators to do good as well as bad.

The source IP address must also be validated to establish itself as legitimate. Next, the bot must also always respect a site's robots.txt file since it has become the standard across most of the web.

“The relationship between Corporate Entrepreneurship, Market Orientation, Organizational Flexibility and Job satisfaction” (PDF) (Dis's.). “Unplanned effects of intelligent agents on Internet use: Social Informatics approach” (PDF).

“Locally noisy autonomous agents improve global human coordination in network experiments”. ^ URL, Simon; You, Chongqing; Centuries, Lionel; Monstrous, Martin (2018).

The protocol defines the specific format of messages exchanged and the sequence of communications for cooperation of the participants. A call established with SIP may consist of multiple media streams, but no separate streams are required for applications, such as text messaging, that exchange data as payload in the SIP message.

SIP is only involved in the signaling operations of a media communication session and is primarily used to set up and terminate voice or video calls. SIP can be used to establish two-party (uni cast) or multiparty (multicast) sessions.

The modification can involve changing addresses or ports, inviting more participants, and adding or deleting media streams. For call setup, the body of a SIP message contains a Session Description Protocol (SDP) data unit, which specifies the media format, codec and media communication protocol.

Voice and video media streams are typically carried between the terminals using the Real-time Transport Protocol (RTP) or Secure Real-time Transport Protocol (SMTP). Every resource of a SIP network, such as user agents, call routers, and voicemail boxes, are identified by a Uniform Resource Identifier (URI).

SIP employs design elements similar to the HTTP request and response transaction model. Each transaction consists of a client request that invokes a particular method or function on the server and at least one response.

SIP reuses most of the header fields, encoding rules and status codes of HTTP, providing a readable text-based format. SIP-based telephony networks often implement call processing features of Signaling System 7 (SS7), for which special SIP protocol extensions exist, although the two protocols themselves are very different.

SIP features are implemented in the communicating endpoints, while the traditional SS7 architecture is in use only between switching centers. The network elements that use the Session Initiation Protocol for communication are called SIP user agents.

However, for network operational reasons, for provisioning public services to users, and for directory services, SIP defines several specific types of network server elements. Each of these service elements also communicates within the client-server model implemented in user agent clients and servers.

The user agent client (UAC) sends SIP requests. The user agent server (UAS) receives requests and returns a SIP response.

Unlike other network protocols that fix the roles of client and server, e.g., in HTTP, in which a web browser only acts as a client, and never as a server, SIP requires both peers to implement both roles. The roles of UAC and UAS only last for the duration of a SIP transaction.

A SIP phone is an IP phone that implements client and server functions of a SIP user agent and provides the traditional call functions of a telephone, such as dial, answer, reject, call hold, and call transfer. SIP phones may be implemented as a hardware device or as a soft phone.

The user agent field is sent in request messages, which means that the receiving SIP server can evaluate this information to perform device-specific configuration or feature activation. Operators of SIP network elements sometimes store this information in customer account portals, where it can be useful in diagnosing SIP compatibility problems or in the display of service status.

A proxy server is a network server with UAC and UAS components that functions as an intermediary entity for the purpose of performing requests on behalf of other network elements. A proxy server primarily plays the role of call routing; it sends SIP requests to another entity closer to its destination.

Proxies are also useful for enforcing policy, such as for determining whether a user is allowed to make a call. A proxy interprets, and, if necessary, rewrites specific parts of a request message before forwarding it.

A redirect server is an user agent server that generates 3xx (redirection) responses to requests it receives, directing the client to contact an alternate set of URIs. It accepts REGISTER requests, recording the address and other parameters from the user agent.

For subsequent requests, it provides an essential means to locate possible communication peers on the network. The location service links one or more IP addresses to the SIP URI of the registering agent.

Multiple user agents may register for the same URI, with the result that all registered user agents receive the calls to the URI. There are two different types of SIP messages: requests and responses.

They are sent by an user agent client to the server, and are answered with one or more SIP responses, which return a result code of the transaction, and generally indicate the success, failure, or other state of the transaction. SIP requests Request nameDescriptionNotesRFC references REGISTERRegister the URI listed in the To-header field with a location server and associates it with the network address given in a Contact header field. The command implements a location service.

RFC3261 Confirm that an entity has received a final response to an Invitation request. RFC3261 CANCELCancel any pending request. Usually means terminating a call while it is still ringing, before answer.

RFC3311 Refers recipient to issue a request for the purpose of call transfer. RFC3428 Infused mid-session information that does not modify the session state. This method is often used for DTMF relay.

It indicates a global failure, including call rejection by the destination. If no response is received after a timer controlled wait period the UAC may choose to terminate the transaction or retransmit the INVITE.

Once a response is received, User1 is confident the INVITE was delivered reliably. SIP defines a transaction mechanism to control the exchanges between participants and deliver messages reliably.

Invite transactions differ in that they can establish a long-running conversation, referred to as a dialog in SIP, and so include an acknowledgment (ACK) of any non-failing final response, e.g., 200 OK. The TTCN-3 test specification language, developed by a task force at ENSI (STF 196), is used for specifying conformance tests for SIP implementations.

When developing SIP software or deploying a new SIP infrastructure, it is important to test capability of servers and IP networks to handle certain call load: number of concurrent calls and number of calls per second. SIP performance tester software is used to simulate SIP and RTP traffic to see if the server and IP network are stable under the call load.

The software measures performance indicators like answer delay, answer/seizure ratio, RTP jitter and packet loss, round-trip delay time. SIP trunking is a similar marketing term preferred for when the service is used to simplify a telecom infrastructure by sharing the carrier access circuit for voice, data, and Internet traffic while removing the need for PRI circuits.

SIP-enabled video surveillance cameras can initiate calls to alert the operator of events, such as motion of objects in a protected area. SIP is used in audio over IP for broadcasting applications where it provides an interoperable means for audio interfaces from different manufacturers to make connections with one another.

SIP-I, Session Initiation Protocol with encapsulated ISP, is a protocol used to create, modify, and terminate communication sessions based on ISP using SIP and IP networks. Services using SIP-I include voice, videotelephony, fax and data.

SIP-I and SIP-T are two protocols with similar features, notably to allow ISP messages to be transported over SIP networks. End-to-end encryption of SIP is only possible if there is a direct connection between communication endpoints.

While a direct connection can be made via Peer-to-peer SIP or via a VPN between the endpoints, most SIP communication involves multiple hops, with the first hop being from an user agent to the useragent's Its. In contrast, the HTTPS protocol provides end-to-end security as it is done with a direct connection and does not involve the notion of hops.

The key exchange for SMTP is performed with Sees (RFC4568), or with RTP (RFC6189). One may also add a MIKEY (RFC3830) exchange to SIP to determine session keys for use with SMTP.

^ Montazerolghaem, AhamdReza; Shekofteh, S.Kane; Chaste, Handle; Naghibzadeh, Mahmoud; Yaghmaee-M, Mohammad-H. (October 2014). “A novel load scheduling for session initiation protocol networks”.

2014 4th International Conference on Computer and Knowledge Engineering (ICC KE). SIP: Understanding the Session Initiation Protocol (Second ed.).

^ Uniform Resource Identifiers (URI): Generic Syntax. ^ Montazerolghaem, Ahmadreza; Hosseini Sent, Said Amino; Rafael, Mohammad Hossein; Tasmanian, Farad (2016-06-01).

“Overload mitigation mechanism for VoIP networks: a transport layer approach based on resource management”. Handbook of algorithms for wireless networking and mobile computing.

^ Porter, Thomas; Andy Mole; Jan Kanclirz; Antonio Rosella (2006). ^ Experiences of Using TTCN-3 for Testing SIP and also DSP (PDF), archived from the original (PDF) on March 30, 2014 “Performance and Stress Testing of SIP Servers, Clients and IP Networks”.

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