The US private sector has been warned to brace for Russian cyberattacks as tensions escalate in Ukraine, Newsweek exclusively reported citing an FBI document, days after cyberattacks were launched against Ukrainian banks and government institutions.

An FBI Liaison Information Report (LIR) dated February 20, provided to Newsweek by a source who wished to remain anonymous, stated, “The FBI Cyber Division, in coordination with the FBI’s Office of Private Sector (OPS), prepared this LIR to inform the private sector about the threat of Russian state-sponsored advanced persistent threat (APT) cyber activities, while tensions with Russia are heightened.”

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“The FBI is engaging in efforts to support the U.S. response and to secure the Homeland from any Russian actions; historically, Russian state-sponsored APT cyber activities increase when tensions are high with Russia,” it added, highlighting the increased threat of cyberattacks with the situation in Ukraine deteriorating.

The report went on to say that the situation in Ukraine “could deteriorate with little notice” due to the “increased threat of Russian military action.”

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“The United States, along with its Allies and partners, has underscored its readiness to impose significant costs on Russia if it takes further military action against Ukraine, potentially further increasing the volume/severity of Russian APT cyber activities,” it added, warning that the cyberattacks against US, Ukraine, and their allies could increase if the situation worsens further.

Russia could target US companies associated with the Pentagon and Ukrainian government institutions, Newsweek further reported, citing a US cyber warfare official who wished to remain anonymous.

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“Russia has targeted clear defense contractors — private companies that support the U.S. military. So this is a normal tactic and we would expect this to be no different in the pre-hostilities for Ukraine. Specifically, any U.S. contractors who are supporting Ukraine’s government and military,” the official told the publication.

The reported FBI warning comes a day after the US confirmed that Russia had been responsible for a series of cyberattacks against Ukrainian banks and government institutions, including the Defense Ministry, the Foreign Ministry, the Culture Ministry, and Ukraine’s two largest state banks.