How does it spread? One of Downadup's most intriguing aspects, say security researchers, is its multipronged attack strategy: It can spread three different ways.
The one that's gotten the most attention exploits a vulnerability in Windows that Microsoft patched nearly four months ago. The bug, which is in a file-sharing service that's included in all versions of the operating system, can be exploited remotely just by sending a malformed data packet to an unpatched PC.
But the worm can also spread by brute-force password attacks, and by copying itself to any removable USB-based devices such as flash drives and cameras. More on those two in a moment.
What machines are most vulnerable to Downadup attack? According to Microsoft, unpatched Windows 2000, Windows XP and Windows Server 2003 machines are at the greatest risk to exploits of the bug patched in October. That gibes with reports from security companies, which have highlighted the danger to PCs running Windows XP Service Pack 2 and XP SP3. Not coincidentally, those versions account for the bulk of Windows' market share.
Unpatched Windows Vista and Server 2008 systems, meanwhile, are less likely to fall victim to attack, since hackers must have authenticated access to the computer, or in other words, know the log-in username and password.
