Variants of the Blaster worm caused havoc to millions

Seattle police charged the youth with "intentionally causing damage and attempting to cause damage to protected computers".

It is thought the youth created the variant, RPCSDBOT, but the extent of infection is not known.

It comes a week after Jeffrey Lee Parson, 18, denied charges of creating another damaging version.

Origin unknown

All versions of the Blaster worm took advantage of a flaw in Microsoft Windows software which had been known about since mid-July.

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The RPCSDBOT variant is thought to have instructed infected computers to launch an attack on a Microsoft update page that would have fixed the flaw.

Microsoft changed its web address to avoid the attack.

The Blaster worm travelled around the net by exploiting a bug in the way many versions of Microsoft Windows handled the transfer of files across the net.

Authorities involved in the Blaster investigation still do not know who created the original worm, which is also known as Lovsan.

The different versions swamped more than 1.2 million computers, and significantly slowed corporate networks worldwide, according to Oliver Friedrichs from the anti-virus firm Symantec.