The company was responding to criticism that it had supported tactics to clamp down on dissent.

The security services in Russia in recent years have seized computers from dozens of outspoken advocacy groups and opposition newspapers, all but disabling them. Law-enforcement officials claim that they are investigating the theft of Microsoft’s intellectual property, but the searches typically happen when those groups are seeking to draw attention to a cause or an event. Allies of the government are rarely if ever investigated for having illegal software on their computers.

The raids have turned into a potent tool to muzzle opposition voices, and private lawyers retained by Microsoft have often bolstered the accusations, asserting that the company was a victim and calling for criminal charges. Until Monday, the company had rebuffed pleas from Russia’s leading human-rights organizations that it refrain from involvement in these cases, saying that it was merely complying with Russian law.

The new Microsoft policy was announced in an apologetic statement by the company’s senior vice president and general counsel, Brad Smith, issued from its headquarters in Redmond, Wash. His statement followed an article in The New York Times on Sunday that detailed piracy cases against prominent advocacy groups and newspapers, including one of Russia’s most influential environmental groups.

Mr. Smith said that Microsoft would make sure that it was no longer offering legal support to politically motivated piracy inquiries by providing a blanket software license to advocacy groups and media outlets. They would be automatically covered by it, without having to apply.

“We want to be clear that we unequivocally abhor any attempt to leverage intellectual property rights to stifle political advocacy or pursue improper personal gain,” Mr. Smith said in a post on the company’s blog. “We are moving swiftly to seek to remove any incentive or ability to engage in such behavior.”

Advocates and journalists who have been targets of such raids said they were pleased that Microsoft was announcing reforms, though some added that they remained suspicious of its intentions. The piracy cases have stirred resentment toward Microsoft in the nonprofit sector in Russia.

In his statement, Mr. Smith appeared to acknowledge that Microsoft needed to address the damage to its image. He said the company would set up a program to offer legal aid to nonprofit groups and media outlets in Russia that are caught up in software inquiries. He also said the company had retained an international law firm to investigate its operations in the country.

With the new, blanket licenses in place, any Microsoft programs on the computers of advocacy groups would carry Microsoft’s seal of approval, making it much harder for the authorities to charge those groups with stealing the company’s software, company executives said.

The licensing plan is intended to last until 2012 but could be extended, Mr. Smith said. The policy could have repercussions beyond Russia because the company indicated that it would apply to other countries as well, though it did not immediately detail which ones.

Microsoft will also step up its efforts to ensure that nonprofit groups and media outlets in Russia have access to a company program that provides Microsoft software at little or no cost. (Mr. Smith said that in the past year alone, the company had donated software with a market value of more than $390 million to over 42,000 nonprofit groups around the world.)

The article in The Times described the case of an environmental group in Siberia, Baikal Environmental Wave, which was raided by the police in January just as it was planning protests against a decision by Prime Minister Vladimir V. Putin to reopen a paper factory that had long polluted Lake Baikal.

Plainclothes officers took 12 computers from Baikal Wave and immediately charged the group with piracy, even though its leaders said they had only licensed Microsoft software. After the raid, the group reached out to Microsoft’s Moscow office, seeking help in defending itself.

Baikal Wave asked Microsoft to confirm that its software was legal, but the company would not, angering the environmentalists. And Microsoft’s local lawyer in Siberia offered testimony to the police in the case on the value of the software that was said to have been stolen.

Prosecutors have not yet decided whether to bring charges against Baikal Wave.

On Monday night, Jennie Sutton, who helped found Baikal Wave two decades ago, said in a telephone interview from Irkutsk that the shift in Microsoft policy might significantly undercut the allegations in the group’s case and any future ones. “This is a victory,” Ms. Sutton said. “If Microsoft is against the police, then it will really look as if the cases that they are bringing are not fair and correct. And they won’t have this as an excuse to try and close us down.”

Dmitri Makarov, an organizer at the Youth Human Rights Movement, said that for months, he had been calling on Microsoft to acknowledge that the private lawyers whom it had retained across Russia had formed unseemly ties to the police.

He said he hoped that under the company’s new policy, the lawyers would never again harass the opposition. “This is what we have been asking for all along,” he said.