The worms infect the mIRC software that lets users join chat groups and have already spread through several countries including the UK, the US and Germany.
The worms (like viruses but hostless and requiring deletion) are called Simpsalapim, a variant of Simpsalapim and Acoragil. They piggyback users joining chat groups by overwriting the user's SCRIPT.INI script file and are triggered by keywords. The worm then throws the user offline or creates other havoc such as adding codes to chat contributions.
Martin Brown, senior technical consultant for Dr Solomon's, said the easiest answer is to change the default save directory to any other directory, thus preventing the worm overwriting the user's default script file.
Brown also predicted that worms on chat channels could become a more frequent pest. "What we've found in the past is that once people have done it once, people jump on the bandwagon. It's probably quite an efficient way of transmitting viruses," he said.
The firm has also put an extra driver on its Web site for users of its WinGuard scanner.
Dr Solomon's: 01296 318700