Last week, a Russian security company reported that as many as 600, 000 Macs, most of them in the United States and Canada, had been infected by Flashback, a Trojan horse virus that infiltrates computers, secretly giving someone else remote access to them.

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Once launched, the virus is designed to install a Trojan horse or backdoor program, and allow investigators to record everything typed into that machine, thereby getting around encryption and passwords.

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Antivirus researchers are examining a new Trojan horse that could pose more of a threat than the Cabir virus, which only spread by Bluetooth (which means Paris Hilton's Sidekick would not, we repeat, would not be vulnerable to the Cabir Trojan).

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Schrader said the best defense against Trojan Horse e-mail viruses is end-user education -- and, of course, updated virus-scanning software.

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