Most of the attention was focused on the big-name Web sites stunned by the denial-of-service attacks. But thousands of computers with constant Internet access also participated inadvertently. The cybervandals planted remote-controlled digital missiles on various other systems, then launched them at the targeted sites.
"I can say with absolute confidence that the vast majority of those corporations do not know that they have been breached," says Simon Perry, director of security at Computer Associates International.
In other words, many, if not most, of the computers that were actually hacked remain compromised. And their users are probably unwittingly going about their business.
Computers most vulnerable to use in DoS attacks have three characteristics, Perry says. They are turned on all of the time and connected to the Internet; they have high bandwidth access; and they are located at places like universities, small businesses, corporations, and, increasingly, in homes with digital subscriber line or cable-modem service.
Hackers scan the Internet looking for computers that are always on and then choose good launch pads. They neither know nor care where those systems are located.
RSA Security has worked on countermeasures for DoS attacks for two years. Its developers contend that detection software and tools might not be enough in this age of increasingly sophisticated and large attacks.
Mathematicians and cryptographers at RSA's labs are working on something called a "client puzzle protocol." It identifies when an attack is mounted (or when network resources are being taxed to such a degree that someone may be attempting an attack). In response, the software sends cryptographic puzzles to each computer requesting entry to a server.
The counterattack software sends one puzzle per request--in effect, turning the flood of malicious traffic back on the computers sending it. Legitimate users seeking server access will be able to solve the puzzles quickly and gain entry with little lag, explains Joe Uniejewski, RSA senior vice president of engineering.
RSA expects to build its client-puzzle method into future products, and plans to offer additional details in coming months.
CA and other vendors offer such tools, which can check systems for Trojan horses, viruses, and other malicious code. Some software can detect when a computer is attacked.
Vigilant use of antivirus software, attack detection software, and the like is the only way to guard against such intrusions, say vendors and security experts.