The most famous among the four people arrested was Sergei Mikhailov, the deputy chief at the FSB’s Information Security Center, which is the FSB’s main unit involved in hunting down hackers. Mikhailov was involved in many cyber investigations. But the community of cyber experts was truly shocked at the arrest of Ruslan Stoyanov, the head of Kaspersky’s computer incidents investigations team. The department he ran consulted the Interior Ministry and the FSB on investigating cyber crime cases. Just before his own arrest, Stoyanov had helped collect evidence in the country’s biggest-ever crackdown on financial hackers, involving the arrest of 50 members of a cyber-crime ring known as Lurk that stole more than 3 billion rubles ($45 million) from banks in Russia and other countries. The group had also exploited weaknesses in how banks connect to Swift, the global payments network, to steal $81 million from Bangladesh’s central bank and $12 million from an Ecuadorean bank.