o a revolution in information processing and transmission," he says. 7.9 E-MAIL "CLUSTER BOMBS" The biggest security threat to PC-based telecom devices, such as laptop com- puters, is e-mail-delivered viruses, worms, and other types of malicious codes. Now it's time to prepare for a fresh Internet scourge-e-mail "cluster bombs." This new online threat, which inundates user e-mail in-boxes with hundreds or thousands of messages in a short period of time, promises to paralyze PDAs and other Internet access devices, says a computer researcher. According to Filippo Menczer, an associate professor of informatics and computer science at Indiana University at Bloomington, a weakness in Web site design makes e-mail cluster bombs possible. The technique is typically employed to target an individual. A miscreant poses as the victim and, using the victim's own e-mail address, fills out Web site forms, such as those used to subscribe to a mailing list. One or two automated messages would hardly overload an e-mail inbox. But software agents, Web crawlers, and scripts can be used by the bomber to fill in thousands of forms almost simultaneously, resulting in a "cluster bomb" of unwanted automatic reply e-mail messages to the victim. The attack can also target a victim's mobile phone with a sudden, large volume of Short Message Service (SMS) messages. "This is a potential danger but also a problem that is easy to fix," says Menczer. "We wanted to let people know how to correct the problem before a hacker or malicious person exploits this vulnerability, causing real damage." The barrage of messages would dominate the bandwidth of an Internet con- nection, making it difficult or impossible for the victim to access the Internet. This is called a distributed denial-of-service attack because a large number of Web sites attack a single target. The attack works because most Web forms do not verify the identity of the people-or automated software-filling them out. But Menczer says there are some simple things Web site managers can do t