348. Adversaries Hide Malicious Scripts Inside Subtitle Files

Hello everyone!

Adversaries may hide malicious content everywhere, including absolutely legitimate files, so today we'll look at the following technique - Obfuscated Files or Information: Steganography (T1027.003).

In some cases threat actors may use quite common malware, but still use some interesting techniques. Just like in this case.

The adversary leveraged malicious LNK files to run a command, which would extract and execute a malicious script from a subtitle file:

cmd.exe /c type Part2.subtitles.srt | more | findstr /n "^" | findstr "100: 101: 102: 103:" | for /f "tokens=1,* delims=:" %a in ('more') do cmd /c %b

Interesting, right? We can hunt for similar activity:

event_type: "processcreatewin"

AND

proc_file_path: "cmd.exe"

AND

cmdline: ("type" AND "findstr" AND *.srt)

See you tomorrow!

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