The US government said Wednesday that its networks have been affected by a "significant cyber incident" and that the attack is "ongoing."
The announcement by the Federal Bureau of Investigation and others followed recent media reports that Russian government hackers have allegedly breached US government agencies during a months-long global espionage campaign.
The FBI, the Cybersecurity and Infrastructure Security Agency and the Office of the Director of National Intelligence said in their statement that they "have become aware of a significant and ongoing cybersecurity campaign" over the course of the past several days.
"As the lead for threat response, the FBI is investigating and gathering intelligence in order to attribute, pursue, and disrupt the responsible threat actors," they said, while noting that they are working to understand the full extent of the campaign.
The Cybersecurity and Infrastructure Security Agency has instructed federal agencies to immediately disconnect from their networks certain versions of software products provided by SolarWinds, a company headquartered in Texas, saying that the products are being "exploited by malicious actors."
Reuters reported earlier this week that hackers believed to be working for Russia have been monitoring internal email traffic at the US Treasury and Commerce departments, citing people who said they feared the hacks uncovered so far may be just the tip of the iceberg.