Software giant Microsoft is offering a $250,000 reward for information leading to the arrest and conviction of hackers behind a powerful computer virus that could lead to millions of PCs being hijacked. Experts have so far been baffled by the true purpose of the Conficker or Downadup virus, but have described its spread as one of the most serious infections ever seen. The worm exploits a bug in Microsoft Windows to infect mainly corporate networks, then — although it has yet to cause any harm — it opens a link back to its point of origin, meaning it can receive further orders to wreak havoc
