The United States has begun talks with Russia and a United Nations arms control committee about strengthening Internet security and limiting military use of cyberspace.

American and Russian officials have different interpretations of the talks so far, but the mere fact that the United States is participating represents a significant policy shift after years of rejecting Russia’s overtures. Officials familiar with the talks said the Obama administration realized that more nations were developing cyberweapons and that a new approach was needed to blunt an international arms race.

In the last two years, Internet-based attacks on government and corporate computer systems have multiplied to thousands a day. Hackers, usually never identified, have compromised Pentagon computers, stolen industrial secrets and temporarily jammed government and corporate Web sites. President Obama ordered a review of the nation’s Internet security in February and is preparing to name an official to coordinate national policy.

Last month, a delegation led by Gen. Vladislav P. Sherstyuk, a deputy secretary of the Russian Security Council and the former leader of the Russian equivalent of the National Security Agency, met in Washington with representatives from the National Security Council and the Departments of State, Defense and Homeland Security. Officials familiar with these talks said the two sides made progress in bridging divisions that had long separated the countries.