A SANS ISC diary entry draws attention to Microsoft Security Research's write-up on the TerminalFix campaign, a multistage intrusion that deploys a reverse tunnel. The diary focuses on one particular aspect: the threat actors' use of PNG image files to hide malicious content.
Steganography lets attackers conceal data inside seemingly harmless image files. In this campaign, the PNG files are part of the infection chain, helping the malware carry out its operations without obvious network-level red flags. The SANS post notes this technique as the element worth examining more closely.
The campaign shows how attackers continue to abuse common file formats to blend in with normal traffic. The SANS diary does not add new technical details beyond Microsoft's research, but it underscores the growing need for defenses that can spot steganographic payloads in enterprise environments.