Microsoft Corp. today said it is offering a $250,000 reward for information that leads to the arrest and conviction of those responsible for launching the “Conficker” computer worm, a threat that has infected millions of Microsoft Windows PCs over the past two months. The reward is the most public acknowledgment yet of the damage inflicted by the Conficker worm – known to some anti-virus companies as “Downadup” — which wiggles into Microsoft systems primarily through a security hole in the Windows operating system. Microsoft issued a software update in late October to help customers guard against the attack, but Conficker can spread even to systems that have already been patched, by piggybacking on removable media — such as USB drives — that launch the worm when connected to a Windows system. “As part of Microsoft’s ongoing security efforts, we constantly look for ways to use a diverse set of tools