Movatterモバイル変換

Network Working Group                                    S. HambridgeRequest for Comments: 2635                                      INTELFYI: 35                                                      A. LundeCategory: Informational                       Northwestern University                                                            June 1999DON'T SPEWA Set of Guidelines for Mass UnsolicitedMailings and Postings (spam*)Status of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (1999).  All Rights Reserved.Abstract   This document explains why mass unsolicited electronic mail messages   are harmful in the Internetworking community.  It gives a set of   guidelines for dealing with unsolicited mail for users, for system   administrators, news administrators, and mailing list managers.  It   also makes suggestions Internet Service Providers might follow.1.  Introduction   The Internet's origins in the Research and Education communities   played an important role in the foundation and formation of Internet   culture.  This culture defined rules for network etiquette   (netiquette) and communication based on the Internet's being   relatively off-limits to commercial enterprise.   This all changed when U.S. Government was no longer the primary   funding body for the U.S. Internet, when the Internet truly went   global, and when all commercial enterprises were allowed to join what   had been strictly research networks.  Internet culture had become   deeply embedded in the protocols the network used.  Although the   social context has changed, the technical limits of the Internet   protocols still require a person to enforce certain limits on   resource usage for the 'Net to function effectively.  Strong   authentication was not built into the News and Mail protocols.  The   only thing that is saving the Internet from congestion collapse is   the voluntary inclusion of TCP backoff in almost all of the TCP/IPHambridge & Lunde            Informational                      [Page 1]

RFC 2635                       DON'T SPEW                      June 1999   driver code on the Internet.  There is no end-to-end cost accounting   and/or cost recovery.  Bandwidth is shared among all traffic without   resource reservation (although this is changing).   Unfortunately for all of us, the culture so carefully nurtured   through the early years of the Internet was not fully transferred to   all those new entities hooking into the bandwidth.  Many of those   entities believe they have found a paradise of thousands of potential   customers each of whom is desperate to learn about stunning new   business opportunities.  Alternatively, some of the new netizens   believe all people should at least hear about the one true religion   or political party or process.  And some of them know that almost no   one wants to hear their message but just can't resist how inexpensive   the net can be to use.  While there may be thousands of folks   desperate for any potential message, mass mailings or Netnews   postings are not at all appropriate on the 'Net.   This document explains why mass unsolicited email and Netnews posting   (aka spam) is bad, what to do if you get it, what webmasters,   postmasters, and news admins can do about it, and how an Internet   Service Provider might respond to it.2.  What is Spam*?   The term "spam" as it is used to denote mass unsolicited mailings or   netnews postings is derived from a Monty Python sketch set in a   movie/tv studio cafeteria.  During that sketch, the word "spam" takes   over each item offered on the menu until the entire dialogue consists   of nothing but "spam spam spam spam spam spam and spam."  This so   closely resembles what happens when mass unsolicited mail and posts   take over mailing lists and netnews groups that the term has been   pushed into common usage in the Internet community.   When unsolicited mail is sent to a mailing list and/or news group it   frequently generates more hate mail to the list or group or apparent   sender by people who do not realize the true source of the message.   If the mailing contains suggestions for removing your name from a   mailing list, 10s to 100s of people will respond to the list with   "remove" messages meant for the originator.  So, the original message   (spam) creates more unwanted mail (spam spam spam spam), which   generates more unwanted mail (spam spam spam spam spam spam and   spam).  Similar occurrences are perpetrated in newsgroups, but this   is held somewhat in check by "cancelbots" (programs which cancel   postings) triggered by mass posting.  Recently, cancelbots have grown   less in favor with those administering News servers since the   cancelbots are now generating the same amount of traffic as spam.   Even News admins are beginning to use filters, demonstrating that   spam spam spam spam spam spam and spam is a monumental problem.Hambridge & Lunde            Informational                      [Page 2]

RFC 2635                       DON'T SPEW                      June 19993.  Why Mass Mailing is Bad   In the world of paper mail we're all used to receiving unsolicited   circulars, advertisements, and catalogs.  Generally we don't object   to this - we look at what we find of interest, and we discard/recycle   the rest.  Why should receiving unsolicited email be any different?   The answer is that the cost model is different.  In the paper world,   the cost of mailing is borne by the sender.  The sender must pay for   the privilege of creating the ad and the cost of mailing it to the   recipient.  An average paper commercial mailing in the U.S.  ends up   costing about $1.00 per addressee.  In the world of electronic   communications, the recipient bears the majority of the cost.  Yes,   the sender still has to compose the message and the sender has to pay   for Internet connectivity.  However, the recipient ALSO has to pay   for Internet connectivity and possibly also connect time charges and   for disk space. For electronic mailings the recipient is expected to   help share the cost of the mailing.  Bulk Internet mail from the U.S.   ends up costing the sender only about 1/100th of a cent per address;   or FOUR ORDERS of magnitude LESS than bulk paper mailings!   Of course, this cost model is very popular with those looking for   cheap methods to get their message out.  By the same token, it's very   unpopular with people who have to pay for their messages just to find   that their mailbox is full of junk mail.  Neither do they appreciate   being forced to spend time learning how to filter out unwanted   messages.  Consider this: if you had to pay for receiving paper mail   would you pay for junk mail?   Another consideration is that the increase in volume of spam will   have an impact on the viability of electronic mail as a   communications medium.  If, when you went to your postal mail box you   found four crates of mail, would you be willing to search through the   crates for the one or two pieces of mail which were not advertising?   Spam has a tremendous potential to create this scenario in the   electronic world.   Frequently spammers indulge in unethical behavior such as using mail   servers which allow mail to be relayed to send huge amounts of   electronic solicitations.  Or they forge their headers to make it   look as if the mail originates from a different domain.  These people   don't care that they're intruding into a personal or business mailbox   nor do they care that they are using other people's resources without   compensating them.   The huge cost difference has other bad effects.  Since even a very   cheap paper mailing is going to cost tens of (U.S.) cents there is a   real incentive to send only to those really likely to be interested.Hambridge & Lunde            Informational                      [Page 3]

RFC 2635                       DON'T SPEW                      June 1999   So paper bulk mailers frequently pay a premium to get high quality   mailing lists, carefully prune out bad addresses and pay for services   to update old addresses.  Bulk email is so cheap that hardly anyone   sending it bothers to do any of this.  As a result, the chance that   the receiver is actually interested in the mail is very, very, very   low.   As of the date of this document, it is a daily event on the Internet   for a mail service to melt-down due to an overload of spam.  Every   few months this happens to a large/major/regional/   national/international service provider resulting in denial of or   severe degradation of service to hundreds of thousands of users.   Such service degradations usually prompt the providers to spend   hundreds of thousands of dollars upgrading their mail service   equipment just because of the volume of spam.  Service providers pass   those costs on to customers.   Doesn't the U.S. Constitution guarantee the ability to say whatever   one likes?  First, the U.S. Constitution is law only in the U.S., and   the Internet is global.  There are places your mail will reach where   free speech is not a given.  Second, the U.S. Constitution does NOT   guarantee one the right to say whatever one likes.  In general, the   U.S. Constitution refers to political freedom of speech and not to   commercial freedom of speech. Finally, and most importantly, the U.S.   Constitution DOES NOT guarantee the right to seize the private   property of others in order to broadcast your speech.  The Internet   consists of a vast number of privately owned networks in voluntary   cooperation.  There are laws which govern other areas of electronic   communication, namely the "junk fax" laws.  Although these have yet   to be applied to electronic mail they are still an example of the   "curbing" of "free speech."  Free speech does not, in general,   require other people to spend their money and resources to deliver or   accept your message.   Most responsible Internet citizens have come to regard unsolicited   mail/posts as "theft of service".  Since the recipient must pay for   the service and for the most part the mail/posts are advertisements   of unsolicited "stuff" (products, services, information) those   receiving it believe that the practice of making the recipient pay   constitutes theft.   The crux of sending large amounts of unsolicited mail and news is not   a legal issue so much as an ethical one.  If you are tempted to send   unsolicited "information" ask yourself these questions: "Whose   resources is this using?"  "Did they consent in advance?"  "What   would happen if everybody (or a very large number of people) did   this?" "How would you feel if 90% of the mail you received was   advertisements for stuff you didn't want?" "How would you feel if 95%Hambridge & Lunde            Informational                      [Page 4]

RFC 2635                       DON'T SPEW                      June 1999   of the mail you received was advertisements for stuff you didn't   want?"  "How would you feel if 99% of the mail you received was   advertisements for stuff you didn't want?"   Although numbers on the volume and rate of increase of spam are not   easy to find, seat-of-the-pants estimates from the people on spam   discussion mailing lists [1] indicate that unsolicited mail/posts   seems to be following the same path of exponential growth as the   Internet as a whole [2].  This is NOT encouraging, as this kind of   increase puts a strain on servers, connections, routers, and the   bandwidth of the Internet as a whole.  On a per person basis,   unsolicited mail is also on the increase, and individuals also have   to bear the increasing cost of increasing numbers of unsolicited and   unwanted mail.  People interested in hard numbers may want to point   their web browsers tohttp://www.techweb.com/se/directlink.cgi?INW19980504S0003 where   Internet Week reports what spam costs.   Finally, sending large volumes of unsolicited email or posting   voluminous numbers of Netnews postings is just plain rude.  Consider   the following analogy: Suppose you discovered a large party going on   in a house on your block.  Uninvited, you appear, then join each   group in conversation, force your way in, SHOUT YOUR OPINION (with a   megaphone) of whatever you happen to be thinking about at the time,   drown out all other conversation, then scream "discrimination" when   folks tell you you're being rude.   To continue the party analogy, suppose instead of forcing your way   into each group you stood on the outskirts a while and listened to   the conversation.  Then you gradually began to add comments relevant   to the discussion.  Then you began to tell people your opinion of the   issues they were discussing; they would probably be less inclined to   look badly on your intrusion.  Note that you are still intruding.   And that it would still be considered rude to offer to sell products   or services to the guests even if the products and services were   relevant to the discussion.  You are in the wrong venue and you need   to find the right one.   Lots of spammers act as if their behavior can be forgiven by   beginning their messages with an apology, or by personalizing their   messages with the recipient's real name, or by using a number of   ingratiating techniques.  But much like the techniques used by Uriah   Heep in Dickens' _David Copperfield_, these usually have an effect   opposite to the one intended.  Poor excuses ("It's not illegal,"   "This will be the only message you receive," "This is an ad," "It's   easy to REMOVE yourself from our list") are still excuses.  Moreover,   they are likely to make the recipient MORE aggravated rather thanHambridge & Lunde            Informational                      [Page 5]

RFC 2635                       DON'T SPEW                      June 1999   less aggravated.   In particular, there are two very severe problems with believing that   a "remove" feature to stop future mail helps: (1) Careful tests have   been done with sending remove requests for "virgin" email accounts   (that have never been used anywhere else).  In over 80% of the cases,   this resulted in a deluge of unsolicited email, although usually from   other sources than the one the remove was sent to.  In other words,   if you don't like unsolicited mail, you should think carefully before   using a remove feature because the evidence is that it will result in   more mail not less.  (2) Even if it did work, it would not stop lots   of new unsolicited email every day from new businesses that hadn't   mailed before.4a. ACK!  I've Been Spammed - Now What?   It's unpleasant to receive mail which you do not want.  It's even   more unpleasant if you're paying for connect time to download it.   And it's really unpleasant to receive mail on topics which you find   offensive.  Now that you're good and mad, what's an appropriate   response?   First, you always have the option to delete it and get on with your   life.  This is the easiest and safest response.  It does not   guarantee you won't get more of the same in the future, but it does   take care of the current problem.  Also, if you do not read your mail   on a regular basis it is possible that your complaint is much too   late to do any good.   Second, consider strategies that take advantage of screening   technology.  You might investigate technologies that allow you to   filter unwanted mail before you see it.  Some software allows you to   scan subject lines and delete unwanted messages before you download   them.  Other programs can be configured to download portions of   messages, check them to see if they are advertising (for example) and   delete them before the whole message is downloaded.   Also, your organization or your local Internet Service Provider may   have the ability to block unwanted mail at their mail relay machines   and thus spare you the hassle of dealing with it at all.  It is worth   inquiring about this possibility if you are the victim of frequent   spam.   Your personal mailer software may allow you to write rules defining   what you do and do not wish to read.  If so, write a rule which sends   mail from the originator of the unwanted mail to the trash.  This   will work if one sender or site repeatedly bothers you.  You may also   consider writing other rules based on other headers if you are sureHambridge & Lunde            Informational                      [Page 6]

RFC 2635                       DON'T SPEW                      June 1999   the probability of them being activated for non-spam is low enough.   That way, although you may still have to pay to download it, you   won't have to read it!   Third, you may consider sending the mail back to the originator   objecting to your being on the mailing-list; however, we recommend   against this.  First, a lot of spammers disguise who they are and   where their mail comes from by forging the mail headers.  Unless you   are very experienced at reading headers discovering the true origin   of the mail will probably prove difficult.  Although you can engage   your local support staff to help you with this, they may have much   higher priorities (such as setting up site-wide filters to prevent   spam from entering the site).  Second, responding to this email will   simply verify your address as valid and make your address more   valuable for other (ab)uses (as was mentioned above inSection 3).   Third, even if the two previous things do not happen, very probably   your mail will be directed to the computer equivalent of a black hole   (the bit-bucket).   As of the writing of this document, there are several pieces of   pending legislation in several jurisdictions about the sending of   unsolicited mail and also about forging headers.  If forging of   headers should become illegal, then responding to the sender is less   risky and may be useful.   Certainly we advocate communicating to the originator (as best as you   can tell) to let them know you will NOT be buying any products from   them as you object to the method they have chosen to conduct their   business (aka spam).  Most responses through media other than   electronic mail (mostly by those who take the time to phone included   "800" (free to calling party in the U.S.) phone numbers) have proved   somewhat effective.  You can also call the business the advertisement   is for, ask to speak to someone in authority, and then tell them you   will never buy their products or use their services because their   advertising mechanism is spam.   Next, you can carbon copy or forward the questionable mail messages   or news postings to your postmaster.  You can do this by sending mail   "To: Postmaster@your-site.example."  Your postmaster should be an   expert at reading mail headers and will be able to tell if the   originating address is forged.  He or she may be able to pinpoint the   real culprit and help close down the site.  If your postmaster wants   to know about unsolicited mail, be sure s/he gets a copy, including   headers.  You will need to find out the local policy and comply.Hambridge & Lunde            Informational                      [Page 7]

RFC 2635                       DON'T SPEW                      June 1999                             *** IMPORTANT ***   Wherever you send a complaint, be sure to include the full headers   (most mail and news programs don't display the full headers by   default).  For mail it is especially important to show the   "Received:" headers.  For Usenet news, it is the "Path:" header.   These normally show the route by which the mail or news was   delivered.  Without them, it's impossible to even begin to tell where   the message originated.  See the appendix for an example of a mail   header.   There is lively and ongoing debate about the validity of changing   one's email address in a Web Browser in order to have Netnews posts   and email look as if it is originating from some spot other than   where it does originate.  The reasoning behind this is that web email   address harvesters will not be getting a real address when it   encounters these.  There is reason on both sides of this debate: If   you change your address, you will not be as visible to the   harvesters, but if you change your address, real people who need to   contact you will be cut off as well.  Also, if you are using the   Internet through an organization such as a company, the company may   have policies about "forging" addresses - even your own!  Most people   agree that the consequences of changing your email address on your   browser or even in your mail headers is fairly dangerous and will   nearly guarantee your mail goes into a black hole unless you are very   sure you know what you are doing.   Finally, DO NOT respond by sending back large volumes of unsolicited   mail.  Two wrongs do not make a right; do not become your enemy; and   take it easy on the network.  While the legal status of spam is   uncertain, the legal status (at least in the U.S.) of a "mail bomb"   (large numbers and/or sizes of messages to the site with the intent   of disabling or injuring the site) is pretty clear: it is criminal.   There is a web site called "www.abuse.net" which allows you to   register, then send your message to the name of the "offending-   domain@abuse.net," which will re-mail your message to the best   reporting address for the offending domain.  The site contains good   tips for reporting abuse netnews or email messages.  It also has some   automated tools that you may download to help you filter your   messages.  Also check CIAC bulletin I-005 at:http://ciac.llnl.gov/ciac/bulletins/i-005c.shtml   or at:http://spam.abuse.net/spam/tools/mailblock.html.Hambridge & Lunde            Informational                      [Page 8]

RFC 2635                       DON'T SPEW                      June 1999   Check the Appendix for a detailed explanation of tools and   methodology to use when trying to chase down a spammer.4b. There's a Spam in My Group!   Netnews is also subject to spamming.  Here several factors help to   mitigate against the propagation of spam in news, although they don't   entirely solve the problem.  Newsgroups and mailing lists may be   moderated, which means that a moderator approves all mail/posts.  If   this is the case, the moderator usually acts as a filter to remove   unwanted and off-topic posts/mail.   In Netnews there are programs which detect posts which have been sent   to multiple groups or which detect multiple posts from the same   source to one group.  These programs cancel the posts.  While these   work and keep unsolicited posts down, they are not 100% effective and   spam in newsgroups seems to be growing at an even faster rate than   spam in mail or on mailing lists.  After all, it's much easier to   post to a newsgroup for which there are thousands of readers than it   is to find individual email addresses for all those folks.  Hence the   development of the "cancelbots" (sometimes called "cancelmoose") for   Netnews groups.  Cancelbots are triggered when one message is sent to   a large number of newsgroups or when many small messages are sent   (from one sender) to the same newsgroup.  In general these are tuned   to the "Breidbart Index" [3] which is a somewhat fuzzy measure of the   interactions of the number of posts and number of groups.  This is   fuzzy purposefully, so that people will not post a number of messages   just under the index and still "get away with it."  And as noted   above, the cancel messages have reached such a volume now that a lot   of News administrators are beginning to write filters rather than   send cancels.  Still spam gets through, so what can a concerned   netizen do?   If there is a group moderator, make sure s/he knows that off-topic   posts are slipping into the group.  If there is no moderator, you   could take the same steps for dealing with news as are recommended   for mail with all the same caveats.   A reasonable printed reference one might obtain has been published by   O'Reilly and Associates, _Stopping Spam_, by Alan Schwartz and Simson   Garfinkel [4].  This book also has interesting histories of spammers   such as Cantor and Siegel, and Jeff Slaton.  It gives fairly clear   instructions for filtering mail and news.Hambridge & Lunde            Informational                      [Page 9]

RFC 2635                       DON'T SPEW                      June 19995.  Help for Beleaguered Admins   As a system administrator, news administrator, local Postmaster, or   mailing-list administrator, your users will come to you for help in   dealing with unwanted mail and posts.  First, find out what your   institution's policy is regarding unwanted/unsolicited mail.  It is   possible that it won't do anything for you, but it is also possible   to use it to justify blocking a domain which is sending particularly   offensive mail to your users.  If you don't have a clear policy, it   would be really useful to create one.  If you are a mailing-list   administrator, make sure your mailing-list charter forbids off-topic   posts. If your internal-only newsgroups are getting spammed from the   outside of your institution, you probably have bigger security   problems than just spam.   Make sure that your mail and news transports are configured to reject   messages injected by parties outside your domain.  Recently   misconfigured Netnews servers have become subject to hijacking by   spammers.  SMTP source routing <@relay.host:user@dest.host> is   becoming deprecated due to its overwhelming abuse by spammers.  You   should configure your mail transport to reject relayed messages (when   neither the sender nor the recipient are within your domain).  Check:http://www.sendmail.org/   under the "Anti-Spam" heading.   If you run a firewall at your site, it can be configured in ways to   discourage spam.  For example, if your firewall is a gateway host   that itself contains an NNTP server, ensure that it is configured so   it does not allow access from external sites except your news feeds.   If your firewall acts as a proxy for an external news-server, ensure   that it does not accept NNTP connections other than from your   internal network.  Both these potential holes have recently been   exploited by spammers.  Ensure that email messages generated within   your domain have proper identity information in the headers, and that   users cannot forge headers.  Be sure your headers have all the   correct information as stipulated byRFC 822 [5] andRFC 1123 [6].   If you are running a mailing-list, allowing postings only by   subscribers means a spammer would actually have to join your list   before sending spam messages, which is unlikely.  Make sure your   charter forbids any off-topic posts.  There is another spam-related   problem with mailing-lists which is that spammers like to retaliate   on those who work against them by mass-subscribing their enemies to   mailing-lists.  Your mailing-list software should require   confirmation of the subscription, and only then should the address be   subscribed.Hambridge & Lunde            Informational                     [Page 10]

RFC 2635                       DON'T SPEW                      June 1999   It is possible, if you are running a mail transfer agent that allows   it, to block persistant offending sites from ever getting mail into   your site.  However, careful consideration should be taken before   taking that step.  For example, be careful not to block out sites for   which you run MX records!  In the long run, it may be most useful to   help your users learn enough about their mailers so that they can   write rules to filter their own mail, or provide rules and kill files   for them to use, if they so choose.   There is information about how to configure sendmail available at   "www.sendmail.org."  Help is also available at "spam.abuse.net."   Another good strategy is to use Internet tools such as whois and   traceroute to find which ISP is serving your problem site.  Notify   the postmaster or abuse (abuse@offending-domain.example) address that   they have an offender.  Be sure to pass on all header information in   your messages to help them with tracking down the offender.  If they   have a policy against using their service to post unsolicited mail   they will need more than just your say-so that there is a problem.   Also, the "originating" site may be a victim of the offender as well.   It's not unknown for those sending this kind of mail to bounce their   mail through dial-up accounts, or off unprotected mail servers at   other sites.  Use caution and courtesy in your approach to those who   look like the offender.   News spammers use similar techniques for sending spam to the groups.   They have been known to forge headers and bounce posts off "open"   news machines and remailers to cover their tracks.  During the height   of the infamous David Rhodes "Make Money Fast" posts, it was not   unheard of for students to walk away from terminals which were logged   in, and for sneaky folks to then use their accounts to forge posts,   much to the later embarrassment of both the student and the   institution.   One way to lessen problems is to avoid using mail-to URLs on your web   pages.  They allow email addresses to be easily harvested by those   institutions grabbing email addresses off the web.  If you need to   have an email address prevalent on a web page, consider using a cgi   script to generate the mailto address.   Participate in mailing lists and news groups which discuss   unsolicited mail/posts and the problems associated with it.   News.admin.net-abuse.misc is probably the most well-known of these.Hambridge & Lunde            Informational                     [Page 11]

RFC 2635                       DON'T SPEW                      June 19996.  What's an ISP to Do   As an Internet Service Provider, you first and foremost should decide   what your stance against unsolicited mail and posts will be.  If you   decide not to tolerate unsolicited mail, write a clear Acceptable Use   Policy which states your position and delineates consequences for   abuse.  If you state that you will not tolerate use of your resource   for unsolicited mail/posts, and that the consequence will be loss of   service, you should be able to cancel offending accounts relatively   quickly (after verifying that the account really IS being mis-used).   If you have downstreaming arrangements with other providers, you   should make sure they are aware of any policy you set.  Likewise, you   should be aware of your upstream providers' policies.   Consider limiting access for dialup accounts so they cannot be used   by those who spew.  Make sure your mail servers aren't open for mail   to be bounced off them (except for legitimate users).  Make sure your   mail transfer agents are the most up-to-date version (which pass   security audits) of the software.   Educate your users about how to react to spew and spewers.  Make sure   instructions for writing rules for mailers are clear and available.   Support their efforts to deal with unwanted mail at the local level -   taking some of the burden from your system administrators.   Make sure you have an address for abuse complaints.  If complainers   can routinely send mail to "abuse@BigISP.example" and you have   someone assigned to read that mail, workflow will be much smoother.   Don't require people complaining about spam to use some unique local   address for complaints.  Read and use 'postmaster' and 'abuse'.  We   recommend adherence toRFC 2142, _Mailbox Names for Common Services,   Roles and Functions._ [7].   Finally, write your contracts and terms and conditions in such   language that allows you to suspend service for offenders, and so   that you can impose a charge on them for your costs in handling the   complaints their abuse generates and/or terminating their account and   cleaning up the mess they make.  Some large ISPs have found that they   can fund much of their abuse prevention staff by imposing such   charges.  Make sure all your customers sign the agreement before   their accounts are activated.  There is a list of "good" Acceptable   Use Policies and Terms of Service at:http://spam.abuse.net/goodsites/index.html.   Legally, you may be able to stop spammers and spam relayers, but this   is certainly dependent on the jurisdictions involved.  Potentially,   the passing of spam via third party computers, especially if theHambridge & Lunde            Informational                     [Page 12]

RFC 2635                       DON'T SPEW                      June 1999   headers are forged, could be a criminal action depending on the laws   of the particular jurisdiction(s) involved.  If your site is being   used as a spam relay, be sure to contact local and national criminal   law enforcement agencies.  Site operators may also want to consider   bringing civil actions against the spammer for expropriation of   property, in particular the computer time and network bandwidth.  In   addition, when a mailing list is involved, there is a potential   intellectual property rights violation.   There are a few law suits in the courts now which claim spammers   interfered with and endangered network connectivity.  At least one   company is attempting to charge spammers for the use of its networks   (www.kclink.com/spam/).7.  Security Considerations   Certain actions to stop spamming may cause problems to legitimate   users of the net. There is a risk that filters to stop spamming will   unintentionally stop legitimate mail too. Overloading postmasters   with complaints about spamming may cause trouble to the wrong person,   someone who is not responsible for and cannot do anything to avoid   the spamming activity, or it may cause trouble out of proportion to   the abuse you are complaining about.  Be sure to exercise discretion   and good judgment in all these cases.  Check your local escalation   procedure.  The Site Security Handbook [2] can help define an   escalation procedure if your site does not have one defined.   Lower levels of network security interact with the ability to trace   spam via logs or message headers.  Measures to stop various sorts of   DNS and IP spoofing can make this information more reliable.   Spammers can and will exploit obvious security weaknesses, especially   in NNTP servers.  This can lead to denial of service, either from the   sheer volume of posts, or as a result of action taken by upstream   providers.8.  Acknowledgments   Thanks for help from the IETF-RUN working group, and also to all the   spew-fighters.  Specific thanks are due to J.D. Falk, whose very   helpful Anti-spam FAQ proved valuable.  Thanks are also due to the   vigilance of Scott Hazen Mueller and Paul Vixie, who run   spam.abuse.net, the Anti-spam web site.  Thanks also to Jacob Palme,   Chip Rosenthal, Karl Auerbach for specific text: Jacob for the   Security Considerations section, Chip for the configuration   suggestions insection 5, Karl for the legal considerations.  Andrew   Gierth was very helpful with Netnews spam considerations.  And thanks   to Gary Malkin for proofing and formatting.Hambridge & Lunde            Informational                     [Page 13]

RFC 2635                       DON'T SPEW                      June 19999.  References   [1] See for example spam-l@peach.ease.lsoft.com   [2] Fraser, B., "Site Security Handbook", FYI 8,RFC 2196, September       1997.   [3] "Current Spam thresholds and guidelines," Lewis, Chris and Tim       Skirvin,http://www.killfile.org/~tskirvin/faqs/spam.html.   [4] Schwartz, Alan and Simson Garfinkel, "Stopping Spam," O'Reilly       and Associates, 1998.   [5] Crocker, D., "Standard for the format of ARPA Internet text       messages", STD 11,RFC 822, August 1982.   [6] Braden, R., "Requirements for Internet hosts - application and       support", STD 3,RFC 1123, October 1989.   [7] Crocker, D., "Mailbox Names for Common Services, Roles and       Functions",RFC 2142, May 1997.   * Spam is a name of a meat product made by Hormel.  "spam" (no     capitalization) is routinely used to describe unsolicited bulk     email and netnews posts.Hambridge & Lunde            Informational                     [Page 14]

RFC 2635                       DON'T SPEW                      June 199910. Appendix - How to Track Down Spammers   In a large proportion of spams today, complaining to the postmaster   of the site that is the apparent sender of a message will have little   effect because either the headers are forged to disguise the source   of the message, or the senders of the message run their own   system/domain, or both.   As a result, it may be necessary to look carefully at the headers of   a message to see what parts are most reliable, and/or to complain to   the second or third-level Internet providers who provide Internet   service to a problem domain.   In many cases, getting reports with full headers from various   recipients of a spam can help locate the source. In extreme cases of   header forgery, only examination of logs on multiple systems can   trace the source of a message.   With only one message in hand, one has to make an educated guess as   to the source. The following are only rough guidelines.   In the case of mail messages, "Received:" headers added by systems   under control of the destination organization are most likely to be   reliable. You can't trust what the source domain calls itself, but   you can usually use the source IP address since that is determined by   the destination domain's server.   In naive mail forgeries, the "Message-ID:" header may show the first   SMTP server to handle the message and/or the "Received:" headers may   all be accurate, but neither can be relied on.  Be especially wary   when the Received: headers have other headers intermixed.  Normally,   Received: headers are all together in a block, and when split up, one   or the other blocks is probably forged.   In the case of news messages, some part of the Path: header may be a   forgery; only reports from multiple sites can make this clear.  In   naive news forgeries, the "NNTP-Posting-Host:" header shows the   actual source, but this can be forged too.   If a spam message advertises an Internet server like a WWW site, that   server must be connected to the network to be usable.  Therefore that   address can be traced.  It is appropriate to complain to the ISP   hosting a web site advertised in a SPAM, even if the origin of the   spam seems to be elsewhere.  Be aware that the spam could be an   attack on the advertised site; the perpetrator knows the site will be   deluged with complaints and their reputation will be damaged.  Any   spam with an electronic address in it is suspect because most   spammers know they're unwelcome and won't make themselves accessible.Hambridge & Lunde            Informational                     [Page 15]

RFC 2635                       DON'T SPEW                      June 1999   Here is an example mail header:----From friendlymail@209.214.12.258.com Thu Feb 26 20:32:47 1998Received: from clio.sc.intel.com by Ludwig.sc.intel.com (4.1/SMI-4.1)        id AA05377; Thu, 26 Feb 98 20:32:46 PSTReceived: from 209.214.12.258.com (209.214.12.258.com [208.26.102.16])        by clio.sc.intel.com (8.8.6/8.8.5) with ESMTP id UAA29637        for <sallyh@intel.com>; Thu, 26 Feb 1998 20:33:30 -0800 (PST)Received: okX-Sender: promo1@gotosportsbook.comX-Advertisement: <a href="http://www.opt-out.com">Click here to be removed.Date: Thu, 26 Feb 1998 23:23:03 -0500From: Sent By <promo1@gotosportsbook.com>Reply-To: Sent By <promo1@gotosportsbook.com>To: friend@bulkmailerSubject: Ad: FREE $50 in Sportsbook & CasinoX-Mailer: AK-Mail 3.0b [eng] (unregistered)Mime-Version: 1.0Content-Type: text/plain; charset=us-asciiContent-Transfer-Encoding: 7bitSender: friendlymail@aqua.258.comMessage-Id: <bulk.6508.19980226232535@aqua.258.com>Status: R----   Doing a traceroute on an IP address or DNS address will show what   domains provide IP connectivity from you to that address.   Using whois and nslookup, one can try to determine who is   administratively responsible for a domain.   In simple cases, a user of a responsible site may be exploiting an   account or a weakness in dial-up security; in those cases a complaint   to a single site may be sufficient. However, it may be appropriate to   complain to more than one domain, especially when it looks like the   spammers run their own system.   If you look at the traceroute to an address, you will normally see a   series of domains between you and that address, with one or more   wide-area/national Internet Service Providers in the middle and   "smaller" networks/domains on either end. It may be appropriate to   complain to the domains nearer the source, up to and including the   closest wide-area ISP.  However, this is a judgement call.   If an intermediate site appears to be a known, responsible domain,   stopping your complaints at this point makes sense.Hambridge & Lunde            Informational                     [Page 16]

RFC 2635                       DON'T SPEW                      June 1999Authors' Information   Sally Hambridge   Intel Corp, SC11-321   2200 Mission College blvd   Santa Clara, CA 95052   EMail: sallyh@ludwig.sc.intel.com   Albert Lunde   Northwestern University   Suite 1400   1603 Orrington Avenue   Evanston, IL 60201   EMail: Albert-Lunde@nwu.eduHambridge & Lunde            Informational                     [Page 17]

RFC 2635                       DON'T SPEW                      June 1999Full Copyright Statement   Copyright (C) The Internet Society (1999).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Hambridge & Lunde            Informational                     [Page 18]