The Islandia, N.Y.-based software firm said it compiled the list from reports tracked by its eTrust Global Antivirus Research Centers.

Code Red, which roused the FBI's attention, failed to make the list. However, Sircam, which has plagued e-mail inboxes for months, took the second slot. In descending order, the other viruses on the list are Magistr, Badtrans.13312, Magistr.B, Hybris.B, MTX, Nimda.A, VBSWG.Generic and Goner.A.

CA said its results indicate that more than 90 percent of 2001's top threats used e-mail as their primary means of propagation, which in turn means that users must take further steps to protect themselves.

"The level of expertise exhibited by virus authors continues to dramatically rise, which means that both the user and antivirus vendor communities must also ratchet up the sophistication of their defensive strategies," said Ian Hameroff, director of antivirus solutions at CA. "One thing is certain -- either people's habits and practices are going to change, or we are going to see more devastation in the coming year."

CA also took the opportunity to remind users of basic safety precautions like installing antivirus software and personal firewalls, updating the antivirus software regularly, deleting e-mail and attachments from unknown senders and being careful about opening attachments in general, regularly updating operating systems and applications, staying informed on the latest threats, and using common sense to avoid cyber-fraud and viruses.