There's been a lot written about viruses and you will of course all have installed protection programs and, if you are on a network, a firewall or even a series of firewalls. You have, haven't you? But you have to hand it to the hackers. They have started circulating bogus warnings about non-existent viruses. Bit pointless, you might say. But invariably the mysterious warning message from a friend tells you to delete the sinisterly named virus files from one or other of your Windows sub-folders. Trouble is that this is invariably a sinisterly named but perfectly legitimate, if obscure, Windows file. One recent one of these was the SULFNBK.EXE hoax. Millions of people hurriedly deleted it from their drives and then, when the hoax was revealed, spent days trying to work out how to re-install it. The final twist was that, at the time of writing, no-one seems to know whether eliminating sulfnbk.exe made the slightest difference to the smooth running of Windows. Then AOL users were urged to delete their AOL softwa re before early June. This was a New Year joke about the prevalence of AOL which got turned into a mid year hoax. There are a couple of rules: the first is that probably all email virus warnings are hoaxes. The second is that if you are worried, check the alleged virus warning out with several of such sites as www.vmyths.com, and www.symantec.com/avcentre/hoax.html which lists such obviously unlikely hoaxes as Get More Money and Gift from Microsoft. And, for Linux users, there's Windows Will Fail On Jan 1. Other such sites are www.stiller.com/hoaxes.html and McAfee's http:vil.mcafee.com/hoax.asp.