Another variant of the MyDoom worm, which spreads by sending copies of itself using its own SMTP engine and harvesting potential e-mail targets from search engines such as Google and Yahoo, was spreading quickly on Thursday.

Antivirus companies are perplexed by a spate of recent viruses that contain messages in which the writers threaten to attack them.

A malicious Trojan horse program has emerged for Pocket PCs, antivirus companies said Thursday, but they characterized the threat as relatively low.

The latest virus, called Bagle.AI by some antivirus companies and Beagle.AG by others, spreads through e-mail as an attached file, which infects a user's PC when opened. The virus is extremely similar to previous versions of the program but uses a different form of compression as a way to dodge virus defenses.

The worm program, dubbed Cabir by Russian antivirus company Kaspersky, apparently uses the Bluetooth short-range wireless feature of smart phones that run the Symbian operating system to detect other Symbian phones, and then transfers itself to the new host as a package file. While able to replicate the spread of the virus in research settings, antivirus companies have not found any evidence that the program is infecting smart phones outside of those limited test cases.

Today's dose of security items includes an Orkut worm, HP's laptop woes; Google ad Trojan and Sun Management Center patches.

Email viruses are so passe, between improved filtering and spreading user awareness, this is a plague that's over - or, at least, that's the received wisdom among pundits.

Antivirus company Sophos warned today of a scheme that invokes Osama bin Laden to convince people to open a file containing a Trojan horse called Hackarmy. The message, which has been posted on several Internet newsgroups, claims to contain pictures taken by CNN journalists of bin Laden committing suicide. But once the supposed picture file is opened, it installs a Trojan horse that effectively recruits the infected machine into the author’s army of "zombie" PCs–already-infected machines that can be controlled surreptitiously from afar. The zombified computers can then be used to distribute spam or launch denial-of-service attacks.