• by Tameka Kee , December 26, 2007

Nearly 9 out of 10 email messages delivered to large enterprises in November were spam, according to the latest stats from Proofpoint. The Sunnyvale, Calif.-based data security company released its Proofpoint Spam Index and found that while overall spam levels dropped slightly (from 89% in October to 88% in November), large companies were still receiving an extremely high volume of spam--with an upsurge in attachment-based spam of almost every kind.

The majority of attachment spam came in the form of images--as image-based spam made up nearly 10% of all unsolicited emails delivered to enterprises in November, up 24% from the previous month. About 5% of all spam came in the form of Microsoft Word (.doc) attachments, a 65% increase over from October. Meanwhile, PDF spam increased by more than 100% from month-over-month, though these kinds of attachments only made up about 2% of enterprise spam overall. MP3 spam was the only category that declined in November, as spammers sent nearly a third less audio file attachments with their messages--representing just 0.04% of total spam volume.

To provide an industry-wide baseline for monitoring rises or declines in spam, the Proofpoint Spam Index aggregates data from the company's email security products in use at enterprises across verticals (including higher education and government agencies).