New variants, dubbed Mytob.EC and EB, are mass mailing worms that spread via email by collecting all addresses stored in an infected computer.

According to security experts, the main characteristics of these worms are that they prevent web users from accessing the websites of security companies and open a backdoor that allows unauthorised and remote hackers to access the system.

The new variants, which also prevent anti-virus applications from updating, arrive in a compressed zip attachment in a message that is normally in English warning surfers of the closure of security or email accounts.

Luis Corrons, director of PandaLabs, said: "We are increasingly seeing new variants of malware that include both the termination of processes associated to antivirus products, and the blocking of the computer's communication with certain websites, such as those through which the antivirus is updated."

To prevent infection by Mytob variants, you should update your anti-virus software against the latest threats and patch against all known security vulnerabilities.

Panda Software

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