The worm Downandup, Conficker, or Kido!, has affected 3.5 million computers with Windows operating systems according to various tech sites.

It targets the vulnerability in Microsoft’s server service which was patched in October 2008. It resets the System Restore point of the affected machine which means that administrators could not delete it.

The article at topnews.us notes that the worm shields itself by disabling Windows security, networking, and updating.

“The vulnerability is potentially wormable on older versions of Windows, XP and earlier; we’re encouraging customers to test and deploy the update as soon as possible,” said a security program manager at Microsoft.

Source: TOPNEWS