Clam AntiVirus is a GPL anti-virus toolkit for UNIX. The main purpose of this software is the integration with mail servers (attachment scanning). The package provides a flexible and scalable multi-threaded daemon, a command line scanner, and a tool for automatic updating via Internet. The programs are based on a shared library distributed with the Clam AntiVirus package, which you can use with your own software. Most importantly, the virus database is kept up to date .

The spam-identification tactics used include:

• 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: again, 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 recognise 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.

The SBL is a realtime database of IP addresses of verified spam sources (including spammers, spam gangs and spam support services), maintained by the Spamhaus Project team and supplied as a free service to help email administrators better manage incoming email streams.

The SBL is queriable in realtime by mail systems thoughout the Internet, allowing email administrators to identify or block incoming connections from IP addresses involved in the sending of Unsolicited Bulk Email.

The SBL database is updated 24/7 by a dedicated international Spamhaus team (US, UK, NL, I, JP, AR) and is broadcast by 32 SBL zone mirror servers based in Australia, Belgium, Denmark, Germany, Greece, Italy, Japan, Netherlands, South Africa, UK and USA. Spamhaus also supplies direct hourly Datafeeds of the SBL to many of the Internet's major Internet Service Providers, Corporations, Universities, Government and Military networks.

The Spamhaus Exploits Block List (XBL) is a realtime database of IP addresses of illegal 3rd party exploits, including open proxies (HTTP, socks, AnalogX, wingate, etc), worms/viruses with built-in spam engines, and other types of trojan-horse exploits.