There were 121 IM attacks in the second quarter compared to 25 in the first quarter of 2005, researchers said.
In June alone, the Akonix Security Center tracked 34 IM network attacks, a few less than May's 39. Researchers tracked variants of existing IM worms such as Kelvir and Opanki as well as three new worms: Aimsend, Harwig, and Pinkton.
Most of the attacks have targeted MSN and AOL's AIM, but most of the ones in June focused on MSN. For every three attacks on MSN, there was about one attack on AIM, according to Akonix.
"The unprecedented increase in the number of threats and the emerging sophistication of instant messaging attacks will continue to create disruption within IT organizations," said Jon Sakoda, chief technology officer of IMlogic. "To ensure instant messaging is productive and secure, companies need to know how to manage it effectively."
The Akonix Security Center compiled the data from the company's internal security group, its enterprise customers, and its partners in messaging and security.
Last month, SC Magazine reported on the rise of viruses in the first half of 2005.