Another variant of the Sasser worm appeared yesterday, despite the arrest of its suspected author last week.
Security specialist Panda Software's PandaLabs unit said the appearance of the variant indicated there is an "organised group of delinquents" engaged in creating and distributing these worms.
The Sasser.E worm exploits the same Microsoft Windows LSASS vulnerability targeted by its predecessors and has already infected millions of computers, according to PandaLabs. The situation is likely to get worse today as people return to work after the weekend.
The worm searches the Internet for vulnerable computers and then copies itself to the Windows directory, leading to a systems error which forces the infected computer to reboot every 60 seconds.
Security company McAfee rated the worm low risk, but noted that it attempts to confuse people trying to remove it by adopting a file named (lsasss.exe) which is very similar to a genuine filename present on most systems.
The same patch that protects against earlier versions of Sasser is also effective against Sasser.E.
Sasser.E also tries to remove any instances of the Bagle worm from users' computers.
"This seems to indicate that there is a kind of cyber-war being waged among the creators of the Bagle, Mydoom, Netsky and Sasser worms, and it will continue to cause many more variants of the virus," said Panda Labs.
David Legard writes for IDG News Service