Microsoft Backs Down

Microsoft Corp. conceded defeat in a high-profile instant-messaging battle with rival America Online Inc., saying that to continue the fight would leave users open to a serious security risk. The dispute has been raging since July, when Microsoft, moving in on a hugely popular Internet phenomenon, unveiled free software that allowed users to send instant messages to each other or to users of AOL’s rival system. AOL, declaring that the Microsoft software essentially hacked into its servers without authorization, blocked the capability, setting off a cat-and-mouse game between software engineers on the two sides. On Wednesday, Microsoft released version 2.0 of its MSN Messenger Service, eliminating the compatibility with AOL’s AIM instant messaging service. Microsoft called on AOL to support a move for a universal standard that would allow users of different software to send instant messages to one another, much as e-mail now has a single standard regardless of client software.