The notorious malware known as the Conficker worm still infects computers, a sort of wild horse with no rider, but investigators appear no closer to finding its creator.
Also known as "Downandup," Conficker was discovered in November 2008, exploiting a vulnerability in Windows XP that allowed remote file execution when file-sharing was enabled. Microsoft patched it a month later.
A souped-up version of Conficker released that year later targeted the autorun feature in XP and Vista. At its peak, Conficker infected upwards of 7 million computers. Microsoft still ranks Conficker as the second-most prevalent malware family on domain-joined computers, according to figures released earlier this year in its Security Intelligence Report Vol. 13