Ident 795195 225026481 2008-07-11T15:02:46Z RussBot 279219 Robot-assisted fix [[WP:DPL|links to disambiguation page]] Hackers {{IPstack}} {{dablink|This article is about the [[Internet]] [[protocol (computing)|protocol]]. For the jargon contraction used in the broadcasting world, see [[station identification]]. For the use of the term ident in aviation, see [[Transponder (aviation)#Ident]].}} The '''Ident Protocol''', specified in RFC 1413, is an [[Internet]] [[protocol (computing)|protocol]] that helps identify the user of a particular [[Transmission Control Protocol|TCP]] [[Telecommunication circuit|connection]]. One popular [[daemon (computer software)|daemon program]] for providing the ident service is '''identd'''. ==How Ident Works== The Ident Protocol is designed to work as a server [[daemon (computer software)|daemon]], on a [[user (computing)|user]]'s computer, where it receives requests to a specified [[TCP and UDP port|port]], generally 113. The server will then send a specially designed response that identifies the username of the current user. ==Usefulness of Ident== Ident is considered useful because it is able to distinguish the name of the person most likely to make a connection to the requesting server, which can then be used as identification for abuse control and/or general reporting purposes. This is useful because on most [[operating systems]] more than one user can be logged in at a time. The protocol is of no help for users where the source of abuse is the computer administrator. The trustworthiness of the ident response can be determined to some extent by seeing if the reverse [[Domain Name System|DNS]] hostname is a typical dynamic [[IP address]] assigned by an [[Internet service provider|ISP]] or a hostname more likely to be of a server. ==Security== The ident protocol is considered dangerous because it allows [[Hacker (computer security)|hackers]] to gain a list of [[username]]s on a [[computer system]] which can later be used for attacks. A generally accepted solution to this is to set up a generic/generated identifier, returning [[Node (networking)|node]] information or even [[gibberish]] (from the requesters point of view) rather than usernames. ==Uses== Ident is important on [[Internet Relay Chat|IRC]] as a large number of people connect to IRC servers via [[Bounce (network)|bouncer]]s which either serve multiple users or are hosted on shared servers. Some users also use clients on [[Unix shell]]s. Without ident there would be no way to ban a single user of a bouncer from a channel or network without banning the entire host running the bouncer. The bouncer operator may also need this information to identify the abusive user. When an IRC server fails to get an identd response it has to fall back on the username given by the client. Ircds usually prefix usernames obtained directly from the client software with a tilde to indicate that they are not ident usernames and may be faked by the user (although with modern single-user home computers, the ident username itself may be set to whatever the user wants and is often returned by the same IRC client as the rest of the client information). Some IRC servers even go as far as blocking clients without an ident response<!-- what a pain in the arse for home unix users -->, the main reason being that it makes it much harder to connect via an "[[open proxy]]" or a system where you have compromised a single account of some form but do not have [[superuser|root]]<!-- unices require root to bind to port numbers < 1024 -->. Special identds are used by those running large numbers of bouncers or a single bouncer that supports multiple users to allow bouncer usernames to be returned rather than simply the name of the user account on the system the bouncer is running under. The best known of these is probably [http://ojnk.sourceforge.net/ oidentd] and [http://www.rndware.info/content/Windows+Ident+Server Windows Ident Server]. ==See also== *Internet Relay Chat ([[Internet Relay Chat|IRC]]) *File Transfer Protocol ([[File Transfer Protocol|FTP]]) *Simple Mail Transfer Protocol ([[Simple Mail Transfer Protocol|SMTP]]) *Network News Transfer Protocol ([[Network News Transfer Protocol|NNTP]]) *Secure Shell ([[Secure Shell|SSH]]) == References == * RFC 912 - Authentication Service * RFC 931 - Authentication Server * [[Daniel J. Bernstein]]: [http://www.watersprings.org/pub/id/draft-bernstein-tap-00.txt TAP] - INTERNET DRAFT [[1992]] * [[Daniel J. Bernstein]]: [ftp://ftp.lysator.liu.se/pub/ident/doc/why-tap.txt Why TAP?] A White Paper, draft 3 920820 * RFC 1413 - Identification Protocol * RFC 1414 - Identification MIB * Peter Eriksson: [ftp://ftp.lysator.liu.se/pub/ident/TAPvsIDENT TAPvsIDENT] 3 Nov [[1993]] * [[Damien Doligez]]: [http://www.geckil.com/~harvest/tcpip-docs/why-encrypt.txt Why encrypt ident/TAP replies?] [[1994]].02.22 == External links == [[Category:Internet protocols]] [[Category:E-mail authentication]] [[cs:Ident]] [[de:Ident]] [[ru:Ident]]