He's 57 now, but gained fame in his 20s when he discovered that a toy whistle in boxes of Cap'n Crunch cereal could trick the telephone network into giving him free calls. Thus the nickname. He moved from telephones into computers. He roamed the world, hacking into computer systems and coding programs for Web sites. He and a partner are trying to build a security business.
Some experts are cautious.
Just because your personal computer at home isn't linked to a network doesn't mean it's immune from attack. It's true that permanently-connected computers are more easily attacked. But e-mail offers a route into any computer any time. Home users can find out if their machines have been captured as zombies by scanning with one of several commercial antivirus programs. Security experts also recommend a personal firewall, a program to block offending or damaging traffic.