Facebook expanded its Anti-Virus Marketplace today with the addition of seven new partners — Avast, AVG, Avira, Kaspersky, Panda, Total Defense, and Webroot. Today's expansion allows users to download anti-virus software from these seven companies, in addition to security apps from existing partners like McAfee and Symantec. The new partners will also add to the database behind Facebook's URL blacklist system, which pre-emptively scans trillions of links for malicious content.

The AV Marketplace originally launched with five partner companies — Microsoft, McAfee, Sophos, Symantec, and Trend Micro — and, in the ensuing six months, has attracted more than 30 million users. By expanding its coalition, Facebook hopes to make its automated security systems even more robust, thereby fostering greater trust among its users.

"Effective security must be a cooperative effort," the company said in a blog post. "By adding these new partners to the Facebook Security family we are sure we can keep our community even better protected from threats both on Facebook and elsewhere on the web."

The AV Marketplace is one of several security features Facebook has incorporated in recent months. In July, the site introduced security "checkpoints" that allow users to voluntarily scan their computers for malware, and in August, it launched a dedicated e-mail address that makes it easier to report phishing.