A newly discovered Russian-language hacker group known as Buhtrap has attacked 13 Russian banks since August using malware that infiltrates their gateway to the central bank, according to Moscow-based cybersecurity company Group-IB. The hackers spread the malware using infected e-mails that mimicked correspondence from the central bank and Gazprombank JSC, Group-IB said in a report Thursday. The program then targeted the automated bank-customer system that connects to the regulator.