Microsoft Corp. has defended its decision to provide search data to federal prosecutors trying to revive an anti-pornography law ruled unconstitutional, saying it "tried to strike the right balance in a very sensitive matter."

Last Thursday, America Online Inc., Microsoft's MSN, Yahoo Inc. and Google Inc. acknowledged that they received subpoenas from the Justice Department, which is trying to revive the 1998 Child Online Protection Act that was struck down by the U.S. Supreme Court. AOL, Microsoft and Yahoo acknowledged handing over search data to the government; Google has refused and intends to fight, saying the Bush administration's requests are too broad.

The day after the disclosure, Microsoft, based in Redmond, Wash., said in its MSN Search Weblog that its actions were consistent with the "principle statement: privacy of our customers is non-negotiable and something worth fighting to protect," said Ken Moss, general manager of MSN Web Search.

Microsoft and the other companies who handed information over to the Justice Department were criticized by some experts as giving in too easily. In defending itself, Microsoft explained that it provided a random sample of pages from its search index and some aggregated query logs that listed queries and how often they occurred.

The data revealed how frequently some query terms occurred, but could not be used to link queries to an IP address or to look for people who queried for specific terms. An IP address is an identifier for a device attached to the Internet.

"Absolutely no personal data was involved," Moss said. In providing the data, the company "tried to strike the right balance in a very sensitive matter."

COPA was meant to shield minors from Web sites that offer sexually explicit content. The high court struck down provisions that required sites to offer such content only to registered users or to people who signed-in first, saying that filtering software is sufficient to keep the content away from children.

In seeking the search data, government lawyers are hoping to show a federal court in Pennsylvania that sexually explicit material is easily accessible through search engines and is not adequately blocked by filters.