He's Mad, He's Bad and He's Got Their Passwords
Not since Hal 9000 toyed so brazenly with Keir Dullea in ''2001: A Space Odyssey'' has a demented product of the computer world posed such a diabolical threat to humankind. In Arthur Kopit's grim and tedious ''Y2K,'' however, it's a mousepad, not a launch pad, that sets the evildoing in motion and the instigator this time is a flesh-and-blood computer geek rather than a collection of circuits gone haywire. The villain of Mr. Kopit's slender play is, in fact, quite a twisted piece of humanity, a hacker who goes by the name of Costa Astrakhan and gets his jollies by breaking into the computer files of a successful New York couple.