Symantec first dismissed the threat, but worm attacks that exploit
a known security hole in the company’s corporate antivirus tool are
proving to be persistent.

The attacks target computers running older versions of Symantec
Client Security and Symantec AntiVirus Corporate Edition. Compromised
systems are turned into remotely controlled zombies by the attacker and used to relay spam and other nefarious activities. Symantec’s Norton consumer software is not affected.

CNet News