Control message

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Control messages are a special kind of Usenet post that are used to control news servers. They differ from ordinary posts by a header field named Control. The body of the field contains control name and arguments.

Contents

There are two historical alternatives to header field Control. They are not supported by contemporary software [1] [2] and forbidden according to RFC 5537. [3] However, the traditional format of the subject line is widely used in addition to the Control header: the subject line consists of the word "cmsg" followed by control name and arguments.

Types

cancel

A cancel message requests the deletion of a specific article. The body of the Control field contains one argument, the Message-ID of the article to delete.

According to RFC 1036 only the author of the target message or the local news administrator is allowed to send a cancel (cancels not meeting this condition are called "rogue cancels"). To verify authorization the From: line (or Sender: line, if it exists) of the cancel message must match the target article. This verification does not work well in modern day Usenet and is rarely used. [4]

Additional hierarchy specific rules (see Breidbart Index) allow cancelbots to send third-party cancels to remove spam.

Example
Control: cancel <899qh19zehlhsdfa@example.com> Subject: cmsg cancel <899qh19zehlhsdfa@example.com>

newgroup

A newgroup message is issued to create a new Usenet newsgroup. The body of the Control field contains one mandatory argument, the name of the new group. The second argument is optional. If present it consists of the keyword moderated. The body of the message typically contains tagline, charter and rationale.

If the group already exists, only the status of the group is changed, i.e. whether it is moderated or nor not. [5]

Typically newgroup messages having a correct digital signature are executed automatically. In some hierarchies (alt.*, free.*, de.alt.*) unsigned newgroup messages just serve as formalized proposal to create a new group. Objections to the proposal are then expressed with a rmgroup. [6] [7]

In many cases newgroup messages are archived by the Internet Systems Consortium. [8]

Example
Control: newgroup comp.object.moderated moderated Subject: cmsg newgroup comp.object.moderated moderated

rmgroup

A rmgroup message is issued to remove a newsgroup. The body of the Control field contains one mandatory argument, the name of the group to remove.

Typically rmgroup messages having a correct digital signature are executed automatically. In some hierarchies unsigned rmgroup messages are used to veto a preceding newgroup.

In the hierarchy de.alt.* removal and creation of groups is handled symmetrically, i.e. an unsigned rmgroup message is used as formalized proposal. Objections to the proposal are then expressed with a newgroup. [7]

Example
Control: rmgroup comp.object.moderated Subject: cmsg rmgroup comp.object.moderated

In 1995 the Church of Scientology attempted to silence criticism by sending mass "rmgroup" messages to Usenet servers targeting alt.religion.scientology, an example of the church's continuing efforts to suppress material critical of Scientology on the Internet. Most servers discarded the message, and those that did not were quickly sent "newgroup" messages reestablishing the newsgroup.

checkgroups

A checkgroups message lists all groups of a hierarchy.

Example
Control: checkgroups Subject: cmsg checkgroups
Example conforming to RFC 5537 
Control: checkgroups de !de.alt #2009021301

Obsolete message types

NameDefinitionDescription
Ihave RFC 850, RFC 1036, RFC 5537 Announce arrival of particular message
Sendme RFC 850, RFC 1036, RFC 5537 Request transmission of particular message
Sendsys RFC 850, RFC 1036, RFC 5537 Request email with list of newsgroups sent to each neighbor
Senduuname RFC 850, RFC 5537 Request email with list of all uucp neighbors
Version RFC 850, RFC 1036, RFC 5537 Request email with name and version of Usenet software
Whogets RFC 5537 No description, just declared obsolete

The ihave/sendme protocol was obsoleted by NNTP.

Answering control messages with large emails can be exploited for a Denial of service attack. Thus news servers stopped implementing sendsys long before it was declared obsolete by RFC 5537. [9]

Security considerations

Header field "Approved:"

Messages of type newgroup and rmgroup are ignored unless there is an "Approved" line in the same message header. [10] Newsservers traditionally allow only selected users to send articles with these lines. As long as there were only a handful of Usenet sites this provided sufficient protection against abuse.

Digital signature

The format of "Arpa Internet Text Messages" [11] is the common base for Usenet [12] and E-mail. [13] The format provides no means of authentication. Various extensions adding a digital signature were developed to prevent forgeries.

Signature formatCovered dataUsage
PGP/INLINE arbitrary text NoCeM
PGP/MIME MIME body partsE-mail
S/MIME MIME body partsE-mail
pgpcontrolbody and selected header fieldsnewgroup, rmgroup, checkgroups

For control message a special format is required since the essential information is in the header fields. Pgpcontrol was originally designed for PGP but also works with OpenPGP. [14]

Hierarchy keys

Newsgroup maintenance of the main Usenet hierarchies (Big 8 and regional hierarchies) is done through signed control messages. Each hierarchy has unique key that is guarded by the hierarchy founders (or their successors). Most newsservers are configured to both automatically execute controls signed with the right key and ignore anything else.

Theoretically this system is also applicable to cancel messages. However, it would not only require a key pair for every Usenet user but also that the respective public key is known to every news server. Cancel-lock [ clarification needed ] is much simpler, but neither commonly accepted, nor implemented in popular news servers and newsreaders. [15]

Archiving

Control messages are typically not shown in the target newsgroup. Instead many servers put them into pseudo newsgroups like control. [16]

Google Groups provides no means to read or write control messages. It does not even execute cancels.

The Internet Systems Consortium archives newgroup and rmgroup together as a single file per group [8] and checkgroups as one file per year. [17]

Related Research Articles

A Usenet newsgroup is a repository usually within the Usenet system, for messages posted from users in different locations using the Internet. They are discussion groups and are not devoted to publishing news. Newsgroups are technically distinct from, but functionally similar to, discussion forums on the World Wide Web. Newsreader software is used to read the content of newsgroups.

<span class="mw-page-title-main">Email client</span> Computer program used to access and manage a users email

An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email.

The Great Renaming was a restructuring of Usenet newsgroups that took place in 1987. B News maintainer and UUNET founder Rick Adams is generally considered to be the initiator of the Renaming.

The Usenet newsgroup alt.religion.scientology started in 1991 to discuss the controversial beliefs of Scientology, as well as the activities of the Church of Scientology, which claims exclusive intellectual property rights thereto and is viewed by many as a dangerous cult. The newsgroup has become the focal point of an aggressive battle known as Scientology versus the Internet, which has taken place both online and in the courts.

<span class="mw-page-title-main">News server</span> Type of server software

A news server is a collection of software used to handle Usenet articles. It may also refer to a computer itself which is primarily or solely used for handling Usenet. Access to Usenet is only available through news server providers.

The Network News Transfer Protocol (NNTP) is an application protocol used for transporting Usenet news articles (netnews) between news servers, and for reading/posting articles by the end user client applications. Brian Kantor of the University of California, San Diego, and Phil Lapsley of the University of California, Berkeley, wrote RFC 977, the specification for the Network News Transfer Protocol, in March 1986. Other contributors included Stan O. Barber from the Baylor College of Medicine and Erik Fair of Apple Computer.

<i>alt.*</i> hierarchy Subclass of Usenet newsgroups

The alt.* hierarchy is a major class of newsgroups in Usenet, containing all newsgroups whose name begins with "alt.", organized hierarchically. The alt.* hierarchy is not confined to newsgroups of any specific subject or type, although in practice more formally organized groups tend not to occur in alt.*. The alt.* hierarchy was created by John Gilmore and Brian Reid.

<span class="mw-page-title-main">B News</span> Usenet news server

B News was a Usenet news server developed at the University of California, Berkeley by Matt Glickman and Mary Ann Horton as a replacement for A News. It was used on Unix systems from 1981 into the 1990s and is the reference implementation for the de facto Usenet standard described in RFC 850 and RFC 1036. Releases from 2.10.2 were maintained by UUNET founder Rick Adams.

<span class="mw-page-title-main">Sporgery</span> Posting a flood of articles to a Usenet group, with falsified headers.

Sporgery is the disruptive act of posting a flood of articles to a Usenet newsgroup, with the article headers falsified so that they appear to have been posted by others. The word is a portmanteau of spam and forgery, coined by German software developer, and critic of Scientology, Tilman Hausherr.

X-No-Archive, also known colloquially as xna, is a newsgroup message header field used to prevent a Usenet message from being archived in various servers.

alt.sex is a Usenet newsgroup – a discussion group within the Usenet network – relating to human sexual activity. It was popular in the 1990s. An October 1993 survey by Brian Reid reported an estimated worldwide readership for the alt.sex newsgroup of 3.3 million, that being 8% of the total Usenet readership, with 67% of all Usenet "nodes" carrying the group. At that time, alt.sex had an estimated traffic of 2,300 messages per month.

Newsgroup spam is a type of spam where the targets are Usenet newsgroups.

The Breidbart Index, developed by Seth Breidbart, is the most significant cancel index in Usenet.

NOV, or News Overview, is a widely deployed indexing method for Usenet articles, also found in some Internet email implementations. Written in 1992 by Geoff Collyer, NOV replaced a variety of incompatible indexing schemes used in different client programs, each typically requiring custom modifications to each news server before they could be used. In modern NNTP implementations, NOV is exposed as the XOVER and related commands.

Usenet II was a proposed alternative to the classic Usenet hierarchy, started in 1998. Unlike the original Usenet, it was peered only between "sound sites" and employed a system of rules to keep out spam.

The Big 8 are a group of newsgroup hierarchies established after the Great Renaming, a restructuring of Usenet that took place in 1987. These hierarchies are managed by the Big 8 Management Board. Groups are added through a process of nomination, discussion and voting.

<span class="mw-page-title-main">Conversation threading</span> Grouping of related messages in digital communications

Conversation threading is a feature used by many email clients, bulletin boards, newsgroups, and Internet forums in which the software aids the user by visually grouping messages with their replies. These groups are called a conversation, topic thread, or simply a thread. A discussion forum, e-mail client or news client is said to have a "conversation view", "threaded topics" or a "threaded mode" if messages can be grouped in this manner. An email thread is also sometimes called an email chain.

rec.music.hip-hop is an Internet Usenet newsgroup primarily dedicated to the discussion of rap and hip-hop music. RMHH is one of the longest running newsgroups on Usenet for the discussion of rap and hip-hop, established in 1995.

<span class="mw-page-title-main">Usenet</span> Worldwide computer-based distributed discussion system

Usenet, USENET, or "in full", User's Network, is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was established in 1980. Users read and post messages to one or more topic categories, known as newsgroups. Usenet resembles a bulletin board system (BBS) in many respects and is the precursor to the Internet forums that have become widely used. Discussions are threaded, as with web forums and BBSes, though posts are stored on the server sequentially.

The Meow Wars were an early example of a flame war sent over Usenet which began in 1996 and ended circa 1998. Its participants were known as "Meowers". The war was characterized by posters from one newsgroup "crapflooding", or posting a large volume of nonsense messages, to swamp on-topic communication in other groups. Ultimately, the flame war affected many boards, with Roisin Kiberd writing in Motherboard, a division of Vice, that esoteric Internet vocabulary was created as a result of the Meow Wars.

References

  1. ↑ InterNetNews never supported all.all.ctl[ clarification needed ]. INN version 1.0 was released in 1990.
  2. ↑ "Subject: cmsg" is described only in RFC 1036 (published in December 1987) but not in RFC 850 (published in June 1983). INN dropped this feature with version 2.3. See INN Changes and Upgrade Information (Internet Archive).
  3. ↑ RFC 5537, 5. Control Messages: [...] The presence of a Subject header field starting with the string "cmsg " MUST NOT cause an article to be interpreted as a control message. [...] Likewise, the presence of a <newsgroup-name> ending in ".ctl" in the Newsgroups header field or the presence of an Also-Control header field MUST NOT cause the article to be interpreted as a control message.
  4. ↑ RFC 850 uses the term "local super user" instead of "local news administrator". Son-of-RFC-1036 (this is the colloquial name of an Internet Draft written by Henry Spencer) drops the administrator's cancel altogether. The problem with the verification scheme is that the From: line is trivial to forge and with cancelbots the cancel message often arrives before the target article. Option verifycancels of INN defaults to false.
  5. ↑ Section 5.2.1. of RFC 5537 says: The newgroup control message requests that the specified group be created or, if already existing, that its moderation status or description be changed. The feature is much older, though. For example the manual page of the ctlinnd utility (part of INN) says: If the newsgroup already exists, this is equivalent to the changegroup command.
  6. ↑
  7. 1 2 Regeln für die Einrichtung, Änderung und Entfernung von Usenet-Gruppen
  8. 1 2 ftp://ftp.isc.org/pub/usenet/control/
  9. ↑ Section "3.5. Sendsys" of RFC 1036 includes the following clause: This information is considered public information, and it is a requirement of membership in USENET that this information be provided on request, either automatically in response to this control message, or manually, by mailing the requested information to the author of the message.
  10. ↑ RFC 1036, sections "3.3. Newgroup" and "3.4. Rmgroup". Section "3.7. Checkgroups" does not contain this clause.
  11. ↑ RFC 822, published in August 1982
  12. ↑ RFC 1036, section "2. Message Format"
  13. ↑ RFC 2822, obsoleted RFC 822 in April 2001
  14. ↑ INN already ships with pgpcontrol. The project site ftp://ftp.isc.org/pub/pgpcontrol/ additionally provides instructions on how to set up PGP/OpenPGP and a huge archive of hierarchy keys.
  15. ↑ Cancel-Locks in Usenet articles: draft-ietf-usefor-cancel-lock-01.txt, published in November 1998, expired in May 1999
  16. ↑ INN normally files control messages to the pseudo newsgroup control. However, if a subgroup of control exists that matches the control command, the control message will be filed into that group instead.
  17. ↑ ftp://ftp.isc.org/pub/usenet/control/other.ctl/
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