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Conficker is the poster child for modern malware.
Its original incarnation in late 2008 exploited a vulnerability that had been patched a month earlier, but because many Windows users are slow to apply patches, it was extremely effective.
But its particular genius was the way it used a Windows feature called AutoRun, along with social engineering, to spread like wildfire. As the dialog box above shows, Conficker spread by infecting ubiquitous USB flash drives (another technology that didn’t exist at the beginning of the decade). It convinced unwary users to click an innocent-looking option in the AutoRun dialog box that appeared when a USB drive was inserted into a PC.
To add insult to injury, it then used a simple dictionary attack to find administrator accounts on the network that used pathetically weak passwords like letmein and 123456 and asdfgh and Admin. Turns out there’s a lot of lazy admins out there.
Microsoft’s response in February 2009 included a $250,000 bounty for identifying the Conficker authors. It closed the USB Autorun hole in the initial release of Windows 7 but didn’t deliver the equivalent patch as a Critical update for Windows XP and Vista until early 2011.
Microsoft and a loose amalgamation of security professionals called the Conficker Working Group shut down the Conficker botnet by taking over its command-and-control servers through legal processes. Today, there are still several million Conficker-infected PCs, but their ability to be controlled by evil forces is long gone.