Microsoft is delivering a Windows software update designed to quash once and for all the difficulty of disabling Autorun, a feature that allows the spread of malware through CDs, USB, and other removable media.

The update fixes an unspecified issue that prevents the NoDriveTypeAutoRun registry key from working as expected, Microsoft says. It comes a month after the US Computer Emergency Readiness Team called out Redmond for offering instructions on disabling Autorun that were "not fully effective."

Autorun's convenience has long been offset by the risk it poses. That's been a given since at least 2005 with the advent of the Sony rootkit fiasco, which in large part was enabled by the ability of music CDs to silently install anti-copying software on end users' machines.

In the wake of Conficker, a worm that's infected more than 10 million machines in the past three months, the stakes have never been higher. Among the vectors it uses to spread, Conficker (which also goes by the name Downadup) makes use of USB flash drives and mapped networked drives to propagate to new machines.

This week's update is the same fix that Microsoft made available here last May, so users who have already installed it (and then carried out the instructions that follow) should be safe.

Ironically, Microsoft describes the fix as a "non-security update," and it offers this explanation: "In this case, we are communicating the availability of an update that affects your ability to perform subsequent updates, including security updates. Therefore, this advisory does not address a specific security vulnerability; rather, it addresses your overall security."

We're not sure about that. What we do know is that if this update is the difference between Autorun being enabled or disabled, it will make users infinitely safer, and that can only be a good thing. ®