The Office of the Comptroller of the Currency issued guidelines Friday that spell out how national banks should combat computer hackers.
The agency saw a growing trend of "cyber-terrorism"-people illegally gaining access to the computer systems of financial institutions to destroy or steal sensitive data.
Technology risk can range from minor theft and embezzlement to the "complete destruction of a bank's records or the inability of a bank to process data," the Comptroller's Office warned.
Banks can foil hackers by installing and monitoring intrusion detection systems, which flag attempts to break in to computer networks.
Banks should also monitor employees' use of the Internet, use encryption technology to protect electronic files, and adopt security programs to restrict unauthorized people from working on bank computers.