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SAN FRANCISCO (AFP) - Computer users were being urged to kill a malicious "old school" software worm poised to destroy their files.

Referred to by a host of names including "Kama Sutra", "Grew", and "Blackworm", the "malware" virus has bored into countless computers worldwide and is reportedly programmed to come to life after the clocks signal the start of Friday.

"Make sure you scan today, don't wait to find out if you've been infected," warned computer virus expert David Perry of Tokyo-based Internet security firm Trend Micro. "This is flat-out malicious, destroying files."

The company was providing free real-time virus scans called "Housecall" at its website, trendmicro.com.

The worm traveled the Internet in emails and got into computers when recipients clicked on unsolicited messages bearing sender names such as crazygirl, badboy, wizzard, and sometimes promising sexy content.

The worm was given a "trigger date" of Friday to allow time for it to spread undetected, Perry said.