Conficker

Conficker (also known as Downup, Downadup and Kido) is a computer worm that first showed up in October 2008. It targeted the Microsoft Windows operating system. It is not known where the name "conficker" came from. "Internet experts" have guessed that the name comes from a mix between two different words: "configure" and "ficken", the German word for "fuck".
Conficker was believed to be the worst computer worm since the SQL slammer worm in 2003. It was estimated 15 million computers were infected with Conficker. The virus was supposed to get worse on April 1, 2009, which caused many people to worry about it. However, there were no bad effects.
On 13 February 2009, Microsoft offered a $250,000 USD reward for help with finding and arresting the people who created the computer worm.