Sharp Increase in Virus-Infected Emails and Directory Harvest Attacks

REDWOOD CITY, Calif. -- Postini, the industry's leading provider of email security and management, today announced that the number of virus-infected email messages in May had increased by 381 percent compared to the previous month. Postini's managed email security service protected its customers from 183,968,287 virus-ridden emails in May, the vast majority of which contained the Sober worm (78 percent).

Sober worm traffic reached an all-time high from May 2-5, when the percentage of emails containing the Sober virus (14 percent) was higher than the percentage of legitimate emails (13 percent).

Postini also protected its customers from more than 33 million directory harvest attacks (DHAs), or an average of 243 per customer every day. This is a 30 percent increase compared to April's average of 191 DHAs by spammers against corporate email per day. May 3, one of the most active days for the Sober worm, was also the most active day for DHAs, with 1,620,666 attacks.

"Sober worm traffic in May was staggering, representing a higher percentage of email messages than legitimate emails for a period of four days," said Andrew Lochart, senior director of marketing at Postini. "New viruses and new variants of existing viruses constantly threaten enterprise networks, increasing the need for advanced managed service capabilities to protect the corporate email environment."

The top ten viruses for May were: Virus Name Quantity Detected sober 142,811,816 mytob 14,049,271 netsky 10,927,378 mime 5,613,976 bankfraud 2,512,716 zafi 1,833,049 mydoom 1,356,954 lovgate 1,258,967 bagle 889,627 new malware-e 875,568

Postini's Email Stat Track is available to users at and provides the most up-to-date statistics on the latest viruses, spam and DHA attacks.