Spamguard
Softwink Spamguard © uses several methods to detect spam and malicious e-mail attachments.
The primary piece of software we use is Spamassassin.
This software uses the following techniques to detect spam:
- Header analysis: spammers use a number of tricks to mask their identities, fool you into thinking they've sent a valid mail, or fool you into thinking you must have subscribed at some stage. Spamassassin tries to spot these.
- Text analysis: spam mails often have a characteristic style (to put it politely), and some characteristic disclaimers and CYA text. Spamassassin can spot these, too.
- Blacklists: Spamassassin supports many useful existing blacklists, such as mail-abuse.org, ordb.org, SURBL", and others.
- Learning classifier: Spamassassin uses a Bayesian-like form of probability-analysis classification, so that a user can train it to recognize mails similar to a training set.
- Distributed hash databases: Vipul's Razor, Pyzor and DCC are collaborative spam-tracking databases, which work by taking a signature of spam messages. Since spam typically operates by sending an identical message to hundreds of people, these databases short-circuit this by allowing the first person to receive a spam to add it to the database -- at which point everyone else will automatically block it.
