Security experts say patterns of activity on the Internet could indicate that a new computer worm is about to attack.

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Analysts who have been decoding the computer worm, which is called W32.

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Stuxnet operates as a computer worm.

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In a cunning twist by the virus writers, an e-mail in wide circulation that purportedly offers a "fix" for the Sasser worm actually infects the user's computer with a different virulent worm, known as Netsky-AC.

CNN: Sasser worm rips through Internet

When the worm infects a computer it sends out the "lol" message to the user's contact list.

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In Europe, the computer security company Sophos reported the worm hit all 19 of Britain's Coastguard control centers.

CNN: Sasser worm rips through Internet

That means there's often much more to do than simply install the patch to both stop the worm and make sure other computer systems are not compromised.

CNN: Sasser worm rips through Internet

Computer security firms have seen two variants of this worm circulating online.

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That, computer experts agree, is because the code for this worm is written very poorly.

CNN: Sasser worm rips through Internet

In January 2003 the Microsoft SQL Server worm, known as Slammer, infected a private computer network at David-Besse nuclear power plant in Oak Harbor, Ohio, disabling a safety monitoring system for nearly five hours, says the Nuclear Regulatory Commission.

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While a computer virus requires some sort of human intervention to be launched, such as opening an e-mail, a worm takes off on its own.

CNN: Sasser worm rips through Internet