Stuxnet, the most advanced computer virus ever discovered (by a long way), generally believed to be the first sophisticated example of a virus being used as an international military weapon, just got an upgrade. Most likely from its original authors.
At least, according to Symantec's analysis lab where a recently found version has been dissected on the operating table, it looks like the versions found in the wild "in Europe" were targeted test runs of a new version that was partly recompiled from the original source code which has so far remained secret.
The new version carries a different payload to the original Stuxnet which, it is generally believed, was intended to shut down or disrupt Iranian nuclear facilities. In fact the new version's actual payload is pluggable. Modules can be loaded dynamically from a command and control server located in India.
Duqu, as the new version is called, can read and write files, execute programs, capture keyboard input (to collect passwords) and generally open back doors for later use by the unknown attackers.
Check out the great article on this by Read Write Web and for a quick recap on the original Stuxnet, check this nicely produced - if creepy - video by Hungry Beast in Australia: