SEATTLE — Microsoft's efforts to solve its multibillion-dollar software-piracy problem have landed it in the cross hairs of computer privacy advocates and attorneys in recent weeks.

Two class-action lawsuits are pending, unsubstantiated Big Brother rumors have swirled on tech blogs and consumers are bristling under accusations of piracy — especially those who shelled out hundreds of bucks for what they thought was legitimate software.

At issue, critics say, is not that Microsoft is trying to curb the unlicensed use of its products, but how the software giant is going about it.

Most offensive to privacy advocates is a quiet, daily check-in that sent technical data from a user's computer — such as make, model and Internet Protocol address — to Microsoft's servers. Many users overlooked the check-in, part of Microsoft's anti-piracy program, until after they had installed it.

The company updated the program late last month and it no longer performs the checks daily.

Microsoft, which would not grant an interview on the subject, maintains on its Web site that it is not collecting personally identifiable information and will not use information it does gather to contact users.

Existing Microsoft services, such as the automatic updates through which the anti-piracy software is distributed, already collect similar technical data as a matter of course. And while Microsoft has been spotlighted for the check-ins, the practice is becoming a hallmark of the emerging-software-as-a-service era in computing.

In its latest update to the Mac OS X operating system, Apple included a more-than-once daily check-in feature that calls back to its servers to verify that small downloaded programs are what they appear to be.

Joel Reidenberg, a professor of law and director of Fordham University's Information Law and Policy research center, said, "Almost every piece of software has with it some kind of feature that calls back to the manufacturer's server."

Microsoft's anti-piracy effort has "become a flashpoint because it gives a peek to consumers as to the information sharing that's been taking place that they just didn't know about," he said.