Turla’s New ‘DeliveryCheck’ Backdoor Compromises Ukrainian Defense Sector
On July 20, 2023, reports emerged of a sophisticated .NET-based backdoor known as DeliveryCheck (also referred to as CAPIBAR or GAMEDAY) targeting the defense sector in Ukraine and Eastern Europe. Attributed to the Russian nation-state actor Turla—also recognized by aliases such as Iron Hunter, Secret Blizzard (formerly Krypton), Uroburos, Venomous Bear, and Waterbug—this malware is associated with Russia’s Federal Security Service (FSB). According to the Microsoft threat intelligence team, in partnership with the Computer Emergency Response Team of Ukraine (CERT-UA), DeliveryCheck is distributed through malicious email attachments containing harmful macros. The backdoor maintains persistence via a scheduled task that downloads and executes it in memory. Additionally, it connects to a command-and-control (C2) server to receive instructions, which may include deploying various payloads embedded within XSLT stylesheets. Successful initial accesses are sometimes accompanied by additional malicious activities.