The Ryzhkov Vendetta by Barry Becker

Alexander Leonidovich Ryzhkov, a Russian oligarch and former general in the Russian Military Intelligence Directorate (GRU), runs a covert operation in the Middle East on behalf of his best friend, the prime minister of Russia. Ryzhkov supplies Saudi terrorists with four Russian-made nuclear suitcase bombs and a list of two US cities to target. A CIA operation thwarts the planned attack and kills many Russian operatives, including his brother Sergei Ryzhkov. The oligarch is out for revenge.
Ryzhkov approaches a former CIA station chief and offers him money in exchange for the CIA operatives’ names. Armed with this intelligence, he launched his vendetta, targeting the former CIA operatives Mark Ericksen, now CEO of EyeD4 Systems, his fiancé Kate McDonald, a banking consultant, and Lars Wahlberg, COO of EyeD4 Systems.