- Klez (computer worm)
Klez is a
computer worm that propagates viae-mail . It first appeared in the end of2001 . A number of variants of the worm exist.Klez infects
Microsoft Windows systems, exploiting a vulnerability inInternet Explorer 's Trident layout engine, used by both Microsoft Outlook andOutlook Express to renderHTML mail.The e-mail through which the worm spreads always includes a text portion and one or more attachments. The text portion consists of either an
HTML internal frame tag which causes buggy e-mail clients to automatically execute the worm, or a few lines of text that attempt to induce the recipient to execute the worm by opening the attachment (sometimes by claiming that the attachment is a patch from Microsoft; sometimes by claiming that the attachment is an antidote for the Klez worm). The first attachment is always the worm, whose internals vary.Once the worm is executed, either automatically by the buggy HTML engine or manually by a naive user, it searches for addresses to send itself to. When it sends itself out, it may attach a file from the infected machine, leading to possible privacy breaches.
Later variants of the worm would use a false "From" address, picking an e-mail address at random from the infected machine's Outlook or Outlook Express address book, making it impossible for casual observers to determine which machine is infected, and making it difficult for experts to determine anything more than the infected machine's Internet Service Provider.
ee also
*
Notable computer viruses and worms
*List of computer viruses
*Computer viruses External links
* [http://www.f-secure.com/v-descs/klez.shtml Anti-virus provider F-Secure Klez information]
* [http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM_KLEZ.H Anti-virus provider Trend Micro Klez information]
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