During the presidency of Viktor Yanukovych, Russia’s FSB was permitted to infiltrate the SBU, and Yanukovych was instructed to curtail Ukrainian counter-espionage activities targeting Russian recruitment in Crimea and Eastern Ukraine. The coup de grâce was administered when Yanukovych fled Kyiv in February 2014: the SBU’s headquarters were ransacked, data on over 22,000 agents and informants were stolen, and every hard drive and flash drive in the building was destroyed. The former SBU Head and his entourage soon surfaced in Moscow. His successor, Valentyn Nalyvaichenko, concluded that Ukraine had lost “everything that forms a basis for a professional intelligence service.”

The Ukrainian case shows the importance Moscow assigns to preventing the emergence of serious counter-intelligence efforts in neighboring states. The same is true in Georgia: when the Georgian government arrested four Russian operatives of Russian military intelligence in 2006, Moscow was so upset at this affirmation of Georgian sovereignty that it curtailed all air, rail, road, and postal links to the country and began harassing Georgian immigrants in Russia.

https://thediplomat.com/2020/01/security-services-moscows-fifth-column-across-eurasia/