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Friday, 19 April, 2002, 15:49 GMT 16:49 UK
Virus returns with a sting in its tail
computer keyboard
Worm first appeared in October
A new variant of a virus called the Klez worm is infecting computers in the UK and US, as well as parts of Asia.

The worm has gradually spread since it was first detected on 15 April, leading most anti-virus companies to classify it as a moderate to high threat.

The virus comes as an attachment to an e-mail with one of 18 subject lines, such as let's be friends and some questions.

The worm has its own mail engine to send itself to every address it finds on an infected machine and also attempts to deactivate some anti-virus products.

One person who contacted BBC News Online said he had received six e-mails with the virus attached.

Devious worm

The virus takes advantage of a known vulnerability in Microsoft Outlook or Outlook Express e-mail programs to trigger itself.

Subject lines used
how are you
your password
eager to see you
meeting notice
look, my beautiful girlfriend
In an attempt to trick users, the virus can also appear as a message warning about the danger of the Klez worm and urging users to execute the attached file.

It also includes a note telling users to ignore any warnings from anti-virus software companies that the attachment is infected.

The new version of the worm contains a second virus called Elkern which attempts to infect all executable files on an infected machine.

Anti-virus experts say home users are more at risk from this worm as they do not update their virus protection as often as businesses.

The new version, the Win32.Klez.H@mm worm, is a variant of the mass-mailing Klez worm that first surfaced in October last year.

The Klez worm reappears periodically, most recently in March, when it caused minimal damage.

See also:

24 Jul 01 | Sci/Tech
Sircam virus steals files
16 Oct 01 | Sci/Tech
Web attacks on the rise
20 Sep 01 | Sci/Tech
Nimda virus 'on the wane'
28 Nov 01 | Sci/Tech
Devious viruses set to grow
18 Dec 01 | Sci/Tech
Warning of malicious e-cards
20 Dec 01 | Sci/Tech
Festive e-greeting hides virus
16 Apr 02 | Sci/Tech
Web attacks on the rise
12 Apr 02 | Sci/Tech
Snapshot shows net under attack
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