The battle against SPAM is waged on two fronts: legal and
technical. Legally, SPAM is not a violation in most governmental regions. In the United States, California leads the fight
against SPAM, deeming SPAM a civil offense and fining spammers up to $50 per SPAM email.
Technically, you can configure Linux to block or otherwise filter SPAM. For example, many SPAM emails forge the delivery
information, which MTAs and MDAs recognize and block. MTAs and MDAs can check information such as the sender's address,
recipient's address, subject, or content for known spammers, known spammer keywords, or any other criteria.
A free framework called the Mail Abuse Prevention System (MAPS) Realtime Blackhole List (RBL)
recipients to blacklist spammers. People who receive SPAM submit a copy of the email to administrators at MAPS RBL. The
administrators decide if the mail is legitimate SPAM, and if so, put the spammer on the MAPS RBLblacklist
SPAM recipients can also complain to their own system administrators. The administrators will analyze the email, and if
legitimate SPAM, add the spammer to local blacklists.
These blacklists hold the IP addresses of known spammers. An MTA can check an incoming email's source IP address against
either the local or the MAPS RBL blacklists and reject mail from a spammer who is on the list.
What's your experience with SPAM? Is it a major annoyance in your life, or a minor inconvenience that you tolerate in order to enjoy the greater advantages of email? Are you or anyone you know a spammer?
The next lesson concludes this module