Finger protocol
Encyclopedia
In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information.
document RFC 742 (December 1977) as an interface to the name and finger programs that provide status reports on a particular computer system or a particular person at network sites. The finger program was written in 1971 by Les Earnest
who created the program to solve the need of users who wanted information on other users of the network. Information on who is logged-in was useful to check the availability of a person to meet. This was probably the earliest form of presence information
for remote network users.
Prior to the finger program, the only way to get this information was with a who
program that showed IDs and terminal line numbers for logged-in users. Earnest named his program after the idea that people would run their fingers down the who list to find what they were looking for.
The Finger user information protocol is based on RFC 1288 (The Finger User Information Protocol, December 1991). Typically the server
side of the protocol is implemented by a program fingerd (for finger daemon
), while the client
side is implemented by the name and finger programs which are supposed to return a friendly, human-oriented status report on either the system at the moment or a particular person in depth. There is no required format, and the protocol consists mostly of specifying a single command line.
The program would supply information such as whether a user is currently logged-on, e-mail address
, full name etc. As well as standard user information, finger displays the contents of the .project and .plan files in the user's home directory
. Often this file (maintained by the user) contains either useful information about the user's current activities, similar to micro-blogging
, or alternatively all manner of humor.
s as a way to initiate a social engineering attack on a company's computer security system. By using a finger client to get a list of a company's employee names, email addresses, phone numbers, and so on, a cracker can telephone or email someone at a company requesting information while posing as another employee. The finger daemon
has also had several exploitable security holes which crackers have used to break into systems. The Morris worm, in 1988, exploited an overflow vulnerability in
(NAT) from the private network address ranges (e.g. 192.168.0.0/16) that are used by the majority of home and office workstations that connect to the Internet through routers or firewalls.
For these reasons, while finger was widely used during the early days of Internet
, by the late 1990s the vast majority of sites on the internet no longer offered the service.
, Unix-like
systems, and current versions of Windows
. Other software has finger support:
Name/Finger protocol
The Name/Finger protocol, written by David Zimmerman, is based on Request for commentsRequest for Comments
In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...
document RFC 742 (December 1977) as an interface to the name and finger programs that provide status reports on a particular computer system or a particular person at network sites. The finger program was written in 1971 by Les Earnest
Les Earnest
Lester Donald Earnest was born in the United States on December 17, 1930. He began his career as a computer programmer in 1954 during a stint as a U.S. Navy Aviation Electronics Officer & Digital Computer Project Officer at Naval Air Development Center, Johnsville, Pennsylvania...
who created the program to solve the need of users who wanted information on other users of the network. Information on who is logged-in was useful to check the availability of a person to meet. This was probably the earliest form of presence information
Presence information
In computer and telecommunications networks, presence information is a status indicator that conveys ability and willingness of a potential communication partner—for example a user--to communicate...
for remote network users.
Prior to the finger program, the only way to get this information was with a who
Who (Unix)
The standard Unix command who displays a list of users who are currently logged into a computer.The who command is related to the command w, which provides the same information but also displays additional data and statistics.- Specification :...
program that showed IDs and terminal line numbers for logged-in users. Earnest named his program after the idea that people would run their fingers down the who list to find what they were looking for.
Finger user information protocol
The finger daemon runs on TCP port 79. The client will (in the case of remote hosts) open a connection to port 79. An RUIP (Remote User Information Program) becomes available on the remote end of the connection to process the request. The local host sends the RUIP one line query based upon the Finger query specification, and waits for the RUIP to respond. The RUIP receives and processes the query, returns an answer, then initiates the close of the connection. The local host receives the answer and the close signal, then proceeds closing its end of the connection.The Finger user information protocol is based on RFC 1288 (The Finger User Information Protocol, December 1991). Typically the server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
side of the protocol is implemented by a program fingerd (for finger daemon
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
), while the client
Client (computing)
A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....
side is implemented by the name and finger programs which are supposed to return a friendly, human-oriented status report on either the system at the moment or a particular person in depth. There is no required format, and the protocol consists mostly of specifying a single command line.
The program would supply information such as whether a user is currently logged-on, e-mail address
E-mail address
An email address identifies an email box to which email messages are delivered. An example format of an email address is lewis@example.net which is read as lewis at example dot net...
, full name etc. As well as standard user information, finger displays the contents of the .project and .plan files in the user's home directory
Home directory
A Home directory is a file system directory on a multi-user operating system containing files for a given user of the system. The specifics of the home directory is defined by the operating system involved; for example, Windows systems between 2000 and 2003 keep home directories in a folder...
. Often this file (maintained by the user) contains either useful information about the user's current activities, similar to micro-blogging
Micro-blogging
Microblogging is a broadcast medium in the form of blogging. A microblog differs from a traditional blog in that its content is typically smaller in both actual and aggregate file size...
, or alternatively all manner of humor.
Security concerns
Supplying such detailed information as e-mail addresses and full names was considered acceptable and convenient in the early days of networking, but later was considered questionable for privacy and security reasons. Finger information has been frequently used by hackerHacker (computer security)
In computer security and everyday language, a hacker is someone who breaks into computers and computer networks. Hackers may be motivated by a multitude of reasons, including profit, protest, or because of the challenge...
s as a way to initiate a social engineering attack on a company's computer security system. By using a finger client to get a list of a company's employee names, email addresses, phone numbers, and so on, a cracker can telephone or email someone at a company requesting information while posing as another employee. The finger daemon
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
has also had several exploitable security holes which crackers have used to break into systems. The Morris worm, in 1988, exploited an overflow vulnerability in
fingerd (among others) to spread. The finger protocol is also incompatible with Network Address TranslationNetwork address translation
In computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
(NAT) from the private network address ranges (e.g. 192.168.0.0/16) that are used by the majority of home and office workstations that connect to the Internet through routers or firewalls.
For these reasons, while finger was widely used during the early days of Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, by the late 1990s the vast majority of sites on the internet no longer offered the service.
Application support
It is implemented on UnixUnix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
, Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
systems, and current versions of Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
. Other software has finger support:
- ELinksELinksELinks is a free text-based console web browser for Unix-like operating systems.It began in late 2001 as an Experimental fork by Petr Baudiš of the Links Web browser, hence the name...
- MinuetMinnesota Internet Users Essential ToolMinnesota Internet Users Essential Tool is an integrated Internet package for DOS Operating Systems on IBM-compatible PCs.-Background:...
External links
- RFC 742 (December 1977)
- RFC 1288 (December 1991)
- Mail from Les Earnest explaining the origin of finger
- Linux finger command
- History of the Finger protocol by Rajiv Shah
- Microsoft TechNet Finger article