Microsoft Corp said on Thursday it found malicious software in its systems related to a massive hacking campaign disclosed by U.S. officials this week, adding a top technology target to a growing list of attacked government agencies.

The Redmond, Washington company is a user of Orion, the widely deployed networking management software from SolarWinds Corp which was used in the suspected Russian attacks on vital U.S. agencies and others.

Microsoft also had its own products leveraged to attack victims, said people familiar with the matter. The U.S. National Security Agency issued a rare “cybersecurity advisory” Thursday detailing how certain Microsoft Azure cloud services may have been compromised by hackers and directing users to lock down their systems.

Microsoft did not immediately respond to questions about the technique.

Still, another person familiar with the matter said the Department of Homeland Security (DHS) does not believe Microsoft was a key avenue of fresh infection.

Both Microsoft and the DHS, which earlier on Thursday said the hackers used multiple methods of entry, are continuing to investigate.

The FBI and other agencies have scheduled a classified briefing for members of Congress Friday.