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                       The U.S. Department of Energy
                    Computer Incident Advisory Capability

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                             INFORMATION BULLETIN


                          E-Mail Spamming countermeasures
                    Detection and prevention of E-Mail spamming

October 20, 1997 19:00 GMT                                        Number I-005
______________________________________________________________________________

PROBLEM:       Unsolicited E-Mail.
PLATFORM:      All platforms which accept E-Mail from the Internet
DAMAGE:        Loss of user productivity and reduction of availability of
               resources.
SOLUTION:      Follow the guidelines outlined below.
______________________________________________________________________________

VULNERABILITY        Programs which implement this type of malicious activity
ASSESSMENT:          are in widespread use. No legal remedies are available
                     yet.
_____________________________________________________________________________

INTRODUCTION:

Spam (aka UCE: Unsolicited Commercial E-Mail) is the Internet version of "Junk
E-Mail." It is an attempt to deliver a message, over the Internet, to someone
who would not otherwise choose to receive it.  Almost all spam is commercial
advertising.  Potential target lists are created by scanning Usenet postings,
stealing Internet mailing lists, or searching the Web for addresses.  Such
information is gathered with automated searches to retrieve E-Mail addresses
for spamming.

The low cost of E-Mail spamming engines offered for sale with millions
of E-Mail addresses, coupled with the fact that the sender does not pay extra
to send E-Mail, has resulted in the current explosive growth of "junk E-Mail."
Currently, unless the spammer offers to sell illegal items, there is no legal
remedy to use to stop E-Mail spammers.

Congress is currently considering legislation to require the marking of
unsolicited commercial E-Mail (UCE), but that legislation is not yet complete.

TERMINOLOGY:
Mail Delivery Agent (MDA). This refers to the program used by the client to
retrieve E-Mail from a storage location. It is usually referred to as the
"mail client." An example of this is pine or eudora.

Mail Transfer Agent (MTA). This refers to the program used running on the
server to store and forward E-Mail messages. It is usually referred to as the
"mail server program." An example of this is sendmail or the server part of
exchange.

CONFIGURATION AND USAGE GUIDELINES:

Mail filtering in the MTA or MDA is the only practical solution today and it
is less than perfect.  There are three primary information sources used to
filter incoming E-Mail :

        - Header Information
        - Mailer Type (a special type of Header information)
        - IP Address (domain name).


Header filtering is performed by scanning the header and/or envelope of a
message, and comparing that information to a list of "filters."  If the
"From", "X-Sender", or "Sender" address is in the "filtering" list, the
message is dropped.  Filtering by E-Mail envelope and/or header information on
the MDA or MTA is the most effective way of limiting spam on your network.
Filtering on the MTA is accomplished by adding rules to the configuration for
the specific mail system running on the server.  The MDA filtering is accomp-
lished through configuration rules in the client uses to read mail.  The most
logical location for filtering is your MTA, since it can perform this service
for a larger number of mail accounts and is a central point for administra-
tion.  The down side to this is that users need to feedback "SPAM" information
to the E-Mail administrators to be incorporated into an organization-wide
filtering list. This requires continuous maintenance to keep the spamming
filters list up-to-date, since it is built in reaction to spamming activity.

Predetermined "filtering" lists are available in the public domain.  Also, if
the spamming filter list is not made with care, valid E-Mail messages may be
discarded along with the spam.

Mailer filtering uses the specific Header information field: "X-mailer."  This
type of filtering enables you to eliminate an entire class of senders --
those who use suspect Mail Delivery Agents.  Some of the more popular MDA's
with spammers are: Pegasus, Floodgate, Extractor, Fusion, MassE-Mail, Quick
Shot, NetMailer, and WorldMerge.  Be aware that, as with other Header
filtering, filtering on "X-mailer" always runs the risk of eliminating
legitimate E-Mail from people using these mailers.  It is the person and not
the mailer that is the problem.

Lastly, you can filter traffic from a domain or range of IP addresses.  This
is probably the easiest way to limit spam from those addresses associated
with spamming.  Again you may also block mail from legitimate users.

SOME DO NOTS

Do NOT spam, mail bomb, or hack spammers.  In many cases the site indicated as
the source of the spamming is not the spammers real site, so attacking that
site is not only wrong, but you are actually "spamming" yourself.

DO NOT Sending "remove" messages to a spammer.  It simply validates your
E-Mail address for future spammings.

Site E-Mail administrators should work closely with their users to make the
list decision about sites, mailers, and senders to be blocked.

Pointers on the actual implementation of filtering methodologies:

    Filtering mail to your personal account
        http://spam.abuse.net/spam/tools/mailblock.html#filters
    Blocking spam E-Mail for an entire site
       http://spam.abuse.net/spam/tools/mailblock.html

    Blocking IP connectivity from spam sites
        http://spam.abuse.net/spam/tools/ipblock.html
______________________________________________________________________________


CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 510-422-8193
    FAX:      +1 510-423-8002
    STU-III:  +1 510-423-2604
    E-Mail:   [email protected]


For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:      http://ciac.llnl.gov/
   Anonymous FTP:       ciac.llnl.gov (198.128.39.53)
   Modem access:        +1 (510) 423-4753 (28.8K baud)
                        +1 (510) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
publications:
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
   availability;
3. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called Majordomo, which ignores E-Mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-Mail message body, substituting
ciac-bulletin, spi-announce OR spi-notes for list-name:

E-Mail to       [email protected] or [email protected]:
        subscribe list-name
  e.g., subscribe ciac-bulletin


You will receive an acknowledgment E-Mail immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the E-Mail.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.


If you include the word 'help' in the body of an E-Mail to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via E-Mail, etc.


PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

X-Persona: 
Date: Tue, 25 Nov 1997 11:37:52 -0800 (PST)
From: [email protected] (CIAC Mail User)
To: [email protected]
Subject: CIAC Statement on Bulletin I-005 - Spamming Countermeasures
Sender: [email protected]

-----BEGIN PGP SIGNED MESSAGE-----


CIAC Bulletin I-005a was directed at alerting users and managers of the
problems with Unsolicited Commercial E-mail (UCE, aka SPAM). In this
bulletin, the Pegasus Mail package was listed among those preferred by
spammers. It has been brought to CIAC's attention that this statement was
incorrect. Pegasus Mail is a legitimate mail package used by ten's of
thousands of legitimate users. Filtering on this mail package IS NOT
advised, as it would restrict legitimate mail from a vast number of
legitimate users. The authors of Pegasus Mail are strongly opposed to SPAM,
and are very proactive in trying to prevent or limit the use of SPAM on the
Internet.

CIAC Bulletin I-005a has been replaced online with Bulletin I-005b. We
will not be resending the complete bulletin.

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Computer Incident Advisory Capability (CIAC)       
(510)422-8193                                   
[email protected]                              
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