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Cancel Messages Frequently Asked Questions Part 1/4 This document contains information about cancel messages on Usenet, such as who is allowed to use them, how they operate, what to do if your message is cancelled, and the like. It does not contain detailed instructions on how to cancel a third party's posts. It is not intended to be a fully technical document; its audience is the average Usenet user, up to a mid-level administrator. This document is not meant to be a comprehensive explanation of Usenet protocols, or of Usenet itself, but a basic knowledge of these concepts is assumed. Please refer to news.announce.newusers, RFC1036, and/or RFC1036bis if you wish to learn them. Disclaimers: The information contained within is potentially hazardous; applying it without the permission of your news administrator may cause the revocation of your account, civil action against you, and even the possibility of criminal lawsuits. The author of this document is in no way liable for misuse of the information contained within, nor is he in any way responsible for damages related to the use or accuracy of the information. Proceed at your own risk. Table of Contents > = In other parts of the FAQ ================= * = Changed since last update I. What are cancel messages? A. What are cancel messages? * B. Are cancel messages the only way to delete a message? C. Where can I find cancel messages? D. Who is generally allowed to issue cancels? * E. When and why are cancel messages allowed? F. How are they issued? G. How do I cancel my own post? * H. Who decided on these rules? II. How do cancels work? A. What is control? control.cancel? How do I receive them? B. What standards are there for cancelling posts? C. What is the format of a cancel message? D. Do all news sites accept all forms of cancels? E. How do I alias out a pseudosite? III. So your post was cancelled... A. Why was my post cancelled? B. I have the cancel message right in front of me. Why was it cancelled? C. But I wasn't doing anything wrong! Why was it cancelled? D. Look, pal, I said I wasn't doing anything wrong, and I meant it. I didn't break any rules that I can see. *Why was my post cancelled?* E. *sigh* Then what do I do about it? >IV. What does it take to cancel messages? >V. That idiot forge-cancelled my posts! >VI. What moral issues are involved with cancel messages? >VII. What's going to happen to cancels in the future? >VIII. What about these other things? >IX. What are the current cancel issues? >Changes >To Do >Contributors >Pointers >Appendix A: Dave the Resurrector >Appendix B: Retromoderation I. What are cancel messages? ============================ A. What are cancel messages? Cancel messages are a specialized form of message to Usenet that, when they arrive at a server, request that the post bearing the Message-ID contained within be deleted. In essence, a cancel message, if heeded, cancels another post. Hence the name. B. Are cancel messages the only way to delete a message? No. Usenet is transitory; not every message will be on all news servers at all times. In fact, cancels are fairly rare; the cause of a missing message is very rarely a cancel. First of all, it takes some period of time for a message to propagate to all news servers that wish to carry the message. This is inherent in the Usenet system; messages take time to arrive. In some cases, they do not arrive at all. More commonly, messages are deleted after a certain period of time so that more messages can take their place - this process is known as expiration. The amount of time that a post exists varies from server to server, and is usually based on the size and content-type of the article and the newsgroups to which it was posted; servers typically save posts for anywhere from a day to several weeks. As this happens on all news servers and is not consistent, expiration is the number one cause of "missing" messages. As time goes on, the software itself has begun to change. Messages posted in HTML, messages containing picture attachments, anything posted more than a few times, even messages with more than about five newsgroups in their headers, all of these are subject to automatic filtering by newer news software; ask your news administrators for details about what is done at your site. Finally, there are more specific causes for missing messages. Your message may have been replaced by another post using a Supersedes: header; your news administrators may be running NoCeM, which selectively deletes posts when used on a server level; your message could have been filtered before it was even posted. Ask your administrators for more information about your system's policies, expiration times, and so forth. In summary: if your post is missing, do not instantly assume that your message was cancelled. A good rule of thumb is "no cancel message, no cancel". If you can find the cancel, then your post was cancelled; if you can't, it probably wasn't. C. Where can I find cancel messages? As you must have a cancel message to show that your message was cancelled, it is a good idea to know where to look for them. The best answer, in the short term, is to search control for the cancel (see section II.A. for details). If you are unable to find them there, the Usenet search engines may be able to help - using Dejanews (<URL:http:// www.dejanews.com>) or AltaVista (<URL:http://www.altavista.com>), search for your email address and the string 'cancel', and you may be able to find any cancels issued for your posts. It should be noted that, for various reasons, the above methods of finding cancel messages are becoming increasingly ineffective. Any suggestions or technical help in solving this problem would be greatly appreciated by the Usenet community. D. Who is generally allowed to issue cancels? In general terms, the only people that are always authorized to issue cancels for a message are the original author of the message and the postmaster at the site the message was posted from. However, there are rules that allow third-party cancels in specific circumstances, such as group moderation, spam and spew cancellations, article forgeries, and a few other limited circumstances; those people in charge of these duties are generally authorized to issue cancels directly relating to the job. E. When and why are cancel messages allowed? When Usenet was created, cancels were meant to be only issued by the original poster of a message. They were implemented so that someone could take back their words, remove information that was no longer accurate, replace inaccurate information, and other, similar purposes. As time went on, more uses for cancel messages have been found. Third party cancellations are now generally allowed if they are not content-based; posting private mail is often more than frowned upon, and newsgroup voting fraud may be stopped with a forged cancel; in the more extreme cases, ads to inappropriate groups are cancelled, threads that are crossposted to too many groups go away, and some even cancel in order to just disrupt a newsgroup. This is not to say that this is accepted; on the contrary, cancelling based on a new criterion is usually more than hotly contested. RFC1036bis, section 7.1, is the most "authoritative" list of valid reasons for cancel messages; however, because it is not a formal RFC and because Usenet changes so quickly, it should not be considered the final word on such matters. The following reasons are probably the most apt to be considered valid by any random news administrator: 1. First person cancels are performed by the original poster of a message. They are explicitly allowed by the news system - a user is always authorized to cancel anything that he or she posts, for any reason, within the limits imposed by his or her administrators, the moderators or maintainers of those groups affected by the cancels, and the user's individual moral code. This authority extends to messages written on another system. 2. Second person cancels are performed by those people officially "in charge" of a user - the user's news administrator, the newsgroup moderators and hierarchy maintainers affected by the user's posts, or any party authorized to act on their behalf by said user or administrator. These cancels, too, are officially authorized. 3. Third person cancels are generally frowned upon, unless they are made based on one of the following criteria: a. Moderator cancels The moderator of a newsgroup has absolute authority over that group. This includes the right to issue cancels for posts that he or she did not authorize. Retromoderation is a subset of this, in which the group is moderated only by the issuing of cancel messages; private hierarchies may generally be considered retromoderated by the hierarchy administrators, while in most most other hierarchies the legitimacy of retromoderation is still up for debate. For more information on creating moderated groups, see news.groups and/or news.groups.questions. b. Spam/EMP cancels Spam or EMP, a message posted to Usenet separately multiple times, is generally accepted as a major threat to Usenet. Therefore, anything posted too many times is automatically cancelled, with no regard to the content of the post. The current spam cancellation threshold is 20 posts; for more information, see the Spam Thresholds FAQ. c. Spew cancels A spew is a long series of similar articles posted over and over again, due either to a malfunctioning program or malicious intent. They are almost universally considered to be a good use for cancels. However, there has yet to be an accepted broad definition of the term "spew" - right now, it mostly fits under "I know it when I see it". For more discussion of spews, see news.admin.net-abuse. policy. d. ECP cancels ECP, or Excessive Cross-Posting, is when a message is posted to too many groups at the same time. Much the same as spam cancellations, if a message is crossposted to too many groups, it will be cancelled without regard to content. Currently, the cancellation threshold is a BI of 20 (the BI is "the sum of the square roots of the number of newsgroups in which each of the postings appears"); as with spam/ EMP cancels, see the Spam Thresholds FAQ for details. e. Binaries in a non-binary group Much of Usenet does not want binary messages, usually for disk space and performance reasons. To accommodate those sites that do want binaries, the alt.binaries.* and comp.binaries.* hierarchies were created. However, there are still some binary messages posted to other Usenet groups; these are often cancelled without regard to content, based on the size of the binary. For more information, see news.admin.net-abuse.policy, where the specifics are being debated. The bincancel FAQ concerns binary cancels in particular. f. Forgeries in the user's name It has become more and more common for people to post messages with false attribution lines. If a message is attributed to a user, they may cancel it or authorize others to cancel it as if they had posted it themselves. F. How are they issued? Cancel messages are sent out as a standard Usenet post, except they contain a "Control: cancel <message-ID>" header. If a system that accepts cancels receives the message, the post with the specified message ID is deleted from that system. Most major newsreaders allow readers to cancel their own posts with a key press. Third-party cancels are more complicated, and must follow several conventions; please refer to section II.B for details. G. How do I cancel my own post? Most major newsreaders allow you to cancel your message with a few keypresses. To cancel your own post, press the following key (depending on your newsreader) while reading your message: Unix rn/trn: 'C' tin: 'D' gnus-emacs: 'C' nn: 'C' slrn: Esc-^C pine: none Unix/X xrn: 'Cancel' button knews: Post/Cancel Article Pan: Articles/Cancel OpenVMS Anu News 'cancel' newsrdr 'cancel' PC/Windows Free Agent - pre-v1.1: Article/Cancel - v1.1+: Message/Cancel Usenet Message Agent - v0.99g,v1.5: Post/Cancel Usenet Message - 1.9 or newer: Post/Cancel Usenet Message - other: Message/Cancel Usenet Message (other versions) Waffle: type CANCEL at the inter-message prompt News Xpress: Article/Cancel Post Turnpike: Article/Cancel Article WinVN: Article/Cancel News Xpress (Win3.1): Article/Cancel Post Anawave Gravity: Article/Cancel Outlook Express: Right Click on Message/Cancel Internet News: File/Cancel Message 40tude Dialog: Post/Cancel Usenet message PC/OS/2 NR/2: Article/Cancel Macintosh Nuntius: Articles/Cancel Article NewsWatcher: Special/Cancel Message MacSOUP: Message/Cancel most browsers: Special/Cancel Message Amiga Thor 2.6: Event Commands/Cancel Message Web Browsers Netscape: Edit/Cancel This Message (most versions 2.0+) Mosaic: none Lynx: none Internet Explorer 4.0: compose/cancel messages Generic/Multi-System Yarn: 'c' If you know of any other news readers that allow cancels, have corrections for any of the above readers, or whatever, please mail firstname.lastname@example.org with the information. H. Who decided on these rules? Usenet is a cooperative venture of many thousands of sites world- wide. It was designed with the principle of mass communication in mind; not much thought was put into security, because it didn't seem necessary at the time. As the need to control the system became evident, so too did the potential for abuse; out of these two needs, these rules grew. As for who actually designed the rules: each site owns its own machines, and can set set policy over its own systems and users. Each site can decide their own expiration policies, what other sites to accept messages from, what control messages they will accept, and so forth; however, it's generally much easier to have a standard set of rules to work with, to improve efficiency and promote some level of consistency across the network. These rules were designed by the system administrators in charge of the systems that Usenet runs on and the users that Usenet serves, in order to give a framework under which to run Usenet as a whole. In short: the rules were made by your administrators and those that they choose to listen to. And if you have any problems with this, you should see if you can make your administrators listen to you. II. How do cancels work? ======================== A. What is control? control.cancel? How do I receive them? control is a pseudo-newsgroup made up of all posts on a news system containing the Control: header, which is used to create or delete newsgroups, perform internal systems checks, cancel posts, and so forth. It is mostly an administrative convenience. On many systems, control is broken up into several components automatically by the software. If this is true, there are several newsgroups: control.newgroup (for the creation of new groups), control.rmgroup (for the removal thereof), control.cancel (for cancel messages), and so forth. If the software is configured this way, cancel messages will appear in control.cancel. All cancels are either recorded in control or control.cancel, depending on the system type. If a post was cancelled recently enough, a record of the cancel *will* be here - if there is no cancel in the group, then either there was no cancel or the cancel message itself has expired (see section I.B.). Unfortunately, the latter situation has become more and more common as time passes. Most major news servers have begun to expire control messages after extremely short time periods, ranging from a couple of days to a couple of hours; even the major Usenet search engines have begun to cut short their cancel message archives. The rule of "no cancel message, no cancel" still holds, but more burden for finding the cancel message is being placed on the reader. If you cannot read control (or control.cancel), ask your news administrator for help. B. What standards are there for cancelling posts? When cancelling your own post, the only standards are the software requirements, which should be done automatically by whatever software you are using. Third-party cancels, however, have certain standards that should be followed. There are three main reasons for following these standards when using third-party cancels. First is to identify the canceller, which gives the practice accountability. The second is to make sure that a particular message is only cancelled once. Finally, some news administrators would rather not accept certain cancels, and a standard will allow them to opt out of the system. The first standard is simple to fulfill; all legitimate third- party cancels include an "X-Cancelled-By:" header, containing the email address where the canceller can be contacted. This also implies that the canceller is willing to respond to comments and complaints; if the mail is simply ignored, the canceller is violating this first standard. The second problem is solved much more creatively. The $alz convention (named after Richard Salz, the creator of INN), specifies that the message ID for a cancel message prepend the message ID of the original message with the string "cancel.". For example: Original Message ID: <email@example.com> Cancel Message ID: <firstname.lastname@example.org> The third problem, that of sites wanting to opt out certain types of cancels, can be solved by adding certain "pseudo-sites" to the path of the cancel; if a particular site wishes to not accept cancels of that type, they can alias out that pseudo-site. For information on how to do this, see section II.E. The commonly accepted pseudo-sites are as follows: cyberspam!usenet Spam/EMP cancels (universal) spewcancel!cyberspam!usenet Spew cancels mmfcancel!cyberspam!usenet Make.Money.Fast cancels bincancel!cyberspam!usenet Binary (in a non-Binary group) cancels adcancel!cyberspam!usenet Ad cancels (for the biz.* hierarchy only) retromod!cyberspam!usenet Retro-Moderation cancels The `!usenet' part denotes that something must come after that part of the path; it is not strictly necessary for it to be `usenet'. Multiple pseudo-sites may be used in one message. For more information on cancel formatting, please refer to the Newsgroup Care Cancel Cookbook by Rosalind Hengeveld <URL:http://www. xs4all.nl/~rosalind/faq-care.html>. C. What is the format of a cancel message? Here's an example, a spam cancel by Chris Lewis, that follows all of the standard conventions (plus a few extras), reformatted to fit into 80 columns: -- Date: 8 Jun 1997 15:43:37 GMT Path: vixen.cso.uiuc.edu!ais.net!newsfeed.direct.ca!News1.Vancouver.iSTAR.net! news.istar.net!n1van.istar!hammer.uoregon.edu!nrchh45.rich.nt.com!bcarh8ac. bnr.ca!despams.ocunix.on.ca!cyberspam!not-for-mail From: email@example.com (Chris Lewis) Approved: firstname.lastname@example.org X-Cancelled-by: email@example.com Sender: Photorep45@ibm.net Newsgroups: alt.recovery.aa Subject: cmsg cancel <firstname.lastname@example.org> Control: cancel <email@example.com> X-No-Archive: Yes X-Spam-Type: WOODSIDE Lines: 7 WOODSIDE spam cancelled by firstname.lastname@example.org Original Subject: Sell YourPhotosNYC.Agency Total spams this type to date: 1.758 Total this spam type for this user: 1041 Total this spam type for this user today: 503 Originating site: internetmci.com Complaint addresses: email@example.com firstname.lastname@example.org -- Points to note: the 'Sender' line matches the original author of the message, while the 'From' line points at the canceller, as does the 'X-Cancelled-By' header. The Message-ID follows the $alz convention, and the proper pseudo-site is present in the 'Path' header. It should also be noted that the 'X-Spam-Type' and 'X-No-Archive' headers are optional, as is all information in the body of the cancel. D. Do all news sites accept cancels? No. Many news sites have decided that, for whatever reason, they do not want cancels; others merely do not want certain types of cancels. Dave Hayes, for example, runs a "Site of Virtue", which not only ignores cancels but drops them without distributing them; patches for INN to do this are available from his Freedom Knights Homepage, at <URL:http://www.jetcafe. org/~dave/usenet/>. America Online, Dejanews, Zippo, and many other news sites do not honor cancels of any sort. E. How do I alias out a pseudosite? INN v1.5 and beyond include shunning mechanisms out of the box; just edit the 'newsfeeds' file and follow the instructions from the comments. Other, older news server software is less likely to include such mechanisms. (If anyone's got information for other news servers, I'd love to include it.) III. So your post was cancelled... ================================== A. Why was my post cancelled? It probably wasn't. Unless you can find a copy of the cancel in control, it is very, *very* unlikely that your post was actually cancelled. Before you begin to worry about a forged cancel, figure out the expiration times for articles on your system and note whether or not your newsreader just refuses to show you articles marked as 'read'; these are the most common causes for "missing" articles. B. I have the cancel message right in front of me. Why was it cancelled? Most cancels nowadays are for cleanup of various forms of net-abuse. If you posted your message to too many places, or too many times, it will generally be cancelled, regardless of the content of the post. For details about what is cancelled and why, read news.admin. net-abuse.usenet, or check the news.admin.net-abuse FAQ. Also, if you received a mail on the subject from a spam cancellers, read it carefully; it should probably explain why your message was cancelled. C. But I wasn't doing anything wrong! Why was it cancelled? There's still legitimate reasons beyond official net-abuse to cancel posts. o The moderator of a moderated newsgroup is permitted to cancel any messages in his newsgroup that he does not approve of. There really isn't much recourse in this case; it's pretty much impossible to impeach a moderator, and the only thing you can really do about their actions is complain for a while or make a competing group. o Individual newsgroups and hierarchies, especially local hierarchies, may have rules permitting them to cancel messages posted there. Again, there isn't much you can do about these cases, beyond reasoning with the administrators and/or not using the hierarchy. o Your post may have inadvertantly triggered the searching criteria for a continuing spam. If you contact the spam-canceller in such a case, you can usually get your post re-posted and can be helped in making sure it won't happen again. o Your postmaster may have decided that they didn't like your post. In this case, the only real recourse you have is to get a new service provider. D. Look, pal, I said I wasn't doing anything wrong, and I meant it. I didn't break any rules that I can see. *Why was my post cancelled?* I don't know. E. *sigh* Then what do I do about it? Post about it to news.admin.net-abuse.usenet. Make sure to include the full headers and text of the cancel, an explanation of what the article was about, and any possible motives for the cancelling that you can think of. The administrators there will, if you're polite, try to help. For more information, read section V. -- Copyright 1998, Tim Skirvin. All rights reserved.