Since we saw the first Sober worm back in October 2003, its author has tried to improve upon tried-and-tested tricks to dupe computer users into launching infected attachments. This latest worm purports to be a warning from CIA and FBI agents, accusing recipients of visiting illegal websites. Mocking the feds is a sure-fire way of goading the authorities, and you can't help but wonder whether the author is desperate to be caught.

It's important to remember that as older threats are vanquished, others will undoubtedly take their place. Mass-mailing worms may be in decline, but it's highly unlikely that they will disappear entirely - the introduction of a major new operating system may even spark a new wave of threats, as virus writers try to find holes in the product.

We advise all companies to consider circulating a policy on virus hoaxes to curb the spread of these annoying emails that can cause mail overload and results in down time and loss of profits. Although they do not cause serious network damage, certain hoaxes, such as the HIV Needle email, are cruel tricks that can be very upsetting for those users receiving them.

There are two re-entries fooling users this month. The Elf Bowling hoax, which has made a festive re-appearance, warns users that the game is infected with a virus and should be deleted immediately upon receipt. This hoax is essentially harmless, but serves as a reminder to companies that they should explain to employees the danger of distributing executable files. The game, while not a malicious threat, can divert employees from doing real work.

If you click on the link, the Web site displays a message saying it is too busy, which may not surprise people who think it might contain genuine breaking news about Michael Jackson.

This is not the first time we have seen immoral opportunists take advantage of a natural disaster to fill their pockets with money meant for victims.