The battle with spam can easily be compared to an arms race. Spammers will
learn about and start exploiting a certain method to send their garbage
messages. E-mail administrators (with the help of open source developers and
vendors) will respond with anti-spam tools battling the latest and "greatest"
spammer methodologies. This seems to be an endless cycle, having yet to reach
an end point.
Some of the more common anti-spam methodologies in use today include (though
this is certainly not an exhaustive list): Header/content checks
(SpamAssassin) Bayesian analysis Sender authentication (Sender Policy
Framework, Yahoo DomainKeys, etc.) Challenge/response (TMDA, Camram) Static
whitelists/blacklists Blackhole listing (SORBS, Kelkea MAPS) Distributed
checksums (DCC, Vipul's Razor) These methods continue to be very useful in
the fight against spam and will likely remain t... (more)
There are many anti-spam solutions available to the e-mail administrator,
resulting in a daunting task when attempting to pick an anti-spam solution.
Some general classifications of anti-spam solutions include (examples in
parentheses):
> Open source (SpamAssassin)
> Standalone commercial applications (Sophos PureMessage for Unix)
> Closely integrated with an existing e-mail solution (McAfee Spamkiller for
Exchange)
> Anti-spam gateway appliance (Ironport X1000)
> Anti-spam service
The line between various anti-spam solutions is very blurry. For example,
many anti-spam gateway ... (more)