To gain entry to a computer the worm exploits a vulnerability in the Internet Explorer security system (the IFRAME vulnerability). Due to this Klez is able to imperceptibly infect computers immediately after the infected message is read. This special feature practically discounts the human factor and many times over raises the effectiveness of Klez.h to infect and to spread.
To protect against Klez.h Kaspersky Labs recommends that you immediately update the Kaspersky Anti-Virus database. To remove the threat of infection from the Klez.h worm and any other modification of this worm, you should install the required patch for Internet Explorer. It can be found on the Microsoft site at the following address:
A more detailed explanation about the Klez worm family can be found in the Kaspersky Virus Encyclopedia at: