Blacklist Patrol
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Blacklist Patrol
Blacklist Patrol proactively monitors major anti-spam blacklists to see if your email server has been listed on any of them.
You're notified daily by email of any blacklists your server is found on.
UK Zombies Blacklisted
Nearly 1,000,000 network addresses under the control of UK ISP Telewest have been listed in the Spam Prevention Early Warning System (SPEWS) database. The SPEWS database is frequently used by mail server administrators for filtering email. The database itself doesn't block any email. System administrators have to manually configure their servers to reference the publicly accessible database.
According to the SPEWS evidence file, the addresses were listed due to excessive zombie spam activity. Zombie computers are systems that have been compromised by malicious software. They are frequently used by spammers to send unwanted email, or by hackers for launching denial of service attacks. Due to the diversity of sending computers, blacklists usually have trouble blocking junk e-mail sent by them.
The malicious software may be delivered by an email worm, an unscrupulous website or security exploit in the user's software. Various Microsoft products seem to be especially vulnerable. In fairness, this is probably at least partially due to how ubiquitously they are deployed.
Telewest acknowledged they have a problem with zombie systems and are working to resolve the issue.
Blacklists work by providing metadata on IP addresses via DNS. A mail server can send the IP address of the emailing computer or server to the blacklist server in the form of a DNS query. An IP address found inside a URL in the email can also be analyzed. The blacklist server then responds with a special IP address indicating if it considers the IP to suspect or not. It's ultimately up to the filtering server or anti-spam mail application whether being on a blacklist is reason enough to block an email.