January 16, 2012

1.1.11 Spam Filter

Spam filter, all-in-one security appliances

A spam filter is a software program that sorts incoming mail in order to identify and pull out unsolicited and unwanted email, also known as spam. Spam filters catch unwanted email and filter it out before it gets delivered internally to a user's inbox. The filtering is done based on rules, e.g. block email coming from certain IP addresses, email that contains particular words in the subject line, and the like. While spam filters are usually used to scan incoming messages, they can also be used to scan outgoing as well and thus act as a quick identifier of internal PCs that may have contracted a virus.

Spam can be used to spread malicious code like viruses and Trojans, and for perpetuating phishing scams. For these reasons and more, a spam filter is a great way to help protect your computer or network and cut out junk mail.

SpamAssassin is a well-known open source spam filter.

Like other types of filtering programs, a spam filter looks for certain criteria on which it bases judgments. From simply scanning subject lines for particular words to more sophisticated methods such as those based on Bayesian statistical methodoloy or other heuristic filters, spam filters attempt to identify spam through suspicious word patterns or word frequency.

References:

  • http://www.wisegeek.com/what-is-a-spam-filter.htm
  • http://searchmidmarketsecurity.techtarget.com/definition/spam-filter
  • CompTIA Security+ Study Guide: Exam SY0-301, Fifth Edition by Emmett Dulaney

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