APT trends report Q1 2021 (DPRK-related paragraph 3)

Kaspersky Securelist

Following up our previous investigation into Lazarus attacks on the defense industry using ThreatNeedle, we discovered another malware cluster named CookieTime used in a campaign mainly focused on the defense industry. We detected activity in September and November 2020, with samples dating back to April 2020. Compared to the already known malware clusters of the Lazarus group, CookieTime shows a different structure and functionality. This malware communicates with the C2 server using the HTTP protocol. In order to deliver the request type to the C2 server, it uses encoded cookie values and fetches command files from the C2 server. The C2 communication takes advantage of steganography techniques, delivered in files exchanged between infected clients and the C2 server. The contents are disguised as GIF image files, but contain encrypted commands from the C2 server and command execution results. We had a chance to look into the command and control script as a result of working closely with a local CERT to take down the threat actor’s infrastructure. The malware control servers are configured in a multi-stage fashion and only deliver the command file to valuable hosts.