Attributed to the cyber criminal group Lazarus, a Mac backdoor Nukesped is seen being delivered to Korean targets via a macro-embedded Microsoft Excel spreadsheet. The macro in this file will just run a PowerShell script that connects to three C&C servers set up by the group. The actual Adobe Flash Player is contained as a hidden Mach-O file. The bundle contains two Flash Player files: a legitimate version and a malicious version (Trojan.MacOS.NUKESPED.B). The app will run the smaller-sized Flash Player as its main executable, which is the malicious version that only poses as a “Flash Player” by name. It also runs the legitimate Flash Player to hide its actual malicious routine. When running the Mac app, the malicious Flash Player will run the legitimate one to play a decoy SWF video. WUhile the video is playing, the malicious Flash Player creates another hidden file (Backdoor.MacOS.NUKESPED.A) in the following path: ~/.FlashUpdateCheck.
Subsequently, a persistence mechanism for this hidden file is installed through dropped PLIST file ~/Library/Launchagents/com.adobe.macromedia.plist.
Further inspection shows that the hidden file ~/.FlashUpdateCheck acts as the dropped Powershell script-equivalent of the Macro-embedded document. This attack type uses an app with a decoy while running the malicious routine to separate the entire Mac attack chain.