WASHINGTON (CN) – The U.S. Treasury Department slapped new sanctions on five Russian companies and three Russian individuals Monday for “malign and destabilizing cyberactivities.”

Treasury Secretary Steven Mnuchin said one of the newly designated Russian firms is controlled by Russia’s primary intelligence agency, the Federal Security Service (FSB), while two others provided the FSB with material and technical support.

Treasury sanctioned the FSB in March and said Monday the newly designated entities pose a threat to the United States and its allies.

In a statement, Treasury Secretary Steven Mnuchin said the work the companies are doing bolsters Russia’s underwater and cyber capabilities.

“The United States is committed to aggressively targeting any entity or individual working at the direction of the FSB whose work threatens the United States and will continue to utilize our sanctions authorities, including those provided under CAATSA, to counter the constantly evolving threats emanating from Russia,” Mnuchin said, abbreviating the Countering America’s Adversaries Through Sanctions Act.

The fresh round of U.S. sanctions from the Trump administration is particularly focused on Russia’s underwater capabilities.

“Russia has been active in tracking undersea communication cables, which carry the bulk of the world’s telecommunications data,” a statement from the Treasury Department says.

The firms designated are Digital Security, ERPScan, Embedi, Kvant Scientific Research Institute and Divetechnoservices.

The three sanctioned individuals – Aleksandr Lvovich Tribun, Oleg Sergeyevich Chirikov and Vladimir Yakovlevich Kaganskiy – are said to have acted on behalf of Divetechnoservices, which supplied diving systems and underwater equipment to Russian agencies, including the FSB.

Monday’s sanctions will block all of their assets within U.S. jurisdiction and prohibit U.S. persons from doing business with them.

The Treasury Department pointed to the cyberattack in Ukraine in June 2017 that tried to disrupt the country’s financial system with ransomeware dubbed NotPetya, which spread through Asia, Europe and the Americas.

Treasury also cited cyber intrusions into the U.S. energy grid that the Treasury Department said could enable future cyberattacks and attacks on network infrastructure, like routers and switches, that could have global reach.