Zombie Spam Hits 62% of Total

Zombie Spam Hits 62% of Total Anti-Spam firm MX Logic claims that Zombie spam now accounts of 62% of all junk email. MX Logic monitors e-mail filtering statistics for messages passing through its servers. This number is up from 44% only a few months ago.

"Zombie spam" is unwanted email that originates from end user systems compromised by malicious mail sending software. The software is usually installed on accident by the user after receiving it in an email messages or as part of a software installation. Sometimes the malware is deployed via a security exploitation.

Zombie spam tends to be highly randomized and is thus difficult to filter. Since it originates from thousands of different networks, traditional DNS blacklists commonly used by antispam programs offer little protection.

Internet service providers are in a position to take action against the problem. ISP's that block outgoing traffic to common SMTP (outgoing email) ports can radically reduce the effectiveness of zombie computers on their networks. By blocking common outgoing mail ports, it in effect blocks all outgoing email sent from those computers. Normal email sent via the ISP's own servers can still be allowed. If more ISPs take these steps, the ones that don't will increasingly be the only networks responsible for zombie spam. Once this happens, DNS blacklists will again become useful for blocking junk e-mail. Currently the problem is too diffuse for this approach to be useful.

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