Skip to main content /TECH with /TECH

Klez.H 'becomes biggest virus'

LONDON, England (CNN) -- The computer virus Klez.H has become the biggest of all time, surpassing SirCam, according to an e-mail security company.

Klez.H, which was first detected on April 15, now affects one in every 300 e-mails, said UK-based MessageLabs on Monday. The company has traced 775,000 copies of the virus so far.

SirCam broke out last summer and maintained an unprecedented growth rate as it replicated itself. That trend has been mirrored by Klez.H, which covers its tracks and deceives recipients, said Alex Shipp from MessageLabs.

Unlike previous viruses like the Love Bug, Klez.H appears as different attachments and with different subject names, making it harder to spot.

It is the eighth version of the virus to be released into cyberspace. A ninth version -- Klez.I -- was launched at the same time but failed to take off. MessageLabs traced only two copies.

Klez.H attacks Windows software, but bypasses Microsoft Outlook e-mail, probably after Microsoft strengthened its anti-virus security, Shipp told CNN.

"Klez.H is able to select random names from address books to use as the sender address, and also creates a large range of subject, text and attachment names, making it difficult to identify and track.

"These elements have meant that the virus has been able to sustain high levels of activity over many weeks and not follow the usual peak and trough pattern that occurs in most outbreak situations.

'When SirCam broke out last summer we thought that we were seeing one of a kind, there was certainly nothing around to match it. However Klez.H has shown us that highly sustainable viruses will continue to appear.

"It is easy to become blase about new viruses as most people are now far more aware of the dangers. In actual fact we are at greater risk then ever."


Note: Pages will open in a new browser window
External sites are not endorsed by CNN Interactive.


Back to the top