Avast study finds 74 percent of all rootkits found on XP PCs were connected to TDL-3/4 (aka ‘Alureon’) The rootkit sits on the master boot record of a PC, which makes it hard to spot and get rid of using conventional tools. XP lacks some of the protection mechanisms that later versions of Windows come with, including Patchguard and driver signing. The last date for extended support has been set as 8 April 2014 leaving at least three years of rootkit exposure for determined users.”]