A fast-moving computer worm Tuesday attacked computer systems using Microsoft operating systems, shutting down computers in the United States, Germany and Asia. Among those hit were offices on Capitol Hill, which is in the midst of August recess, and media organizations, including CNN, ABC and The New York Times. The Caterpillar Co. in Peoria, Illinois, reportedly also had problems. A small number of computers in an administrative office at San Francisco International Airport also crashed, but they were not essential to the airport’s operation, spokesman Mike McCarron said. The FBI said the computer problems did not appear to be part of any widespread attack. While the worm affects primarily Windows 2000, it also can affect some early versions of Microsoft XP, said Johannes Ullrich, chief technology officer of the Sans Institute, a network security firm based in Jacksonville, Florida. Symptoms include the repeated shutdown and rebooting of a computer. Microsoft has a downloadable patch on its security homepage, www.microsoft.com/security.