Detectionhightest

Suspicious Greedy Compression Using Rar.EXE

Detects RAR usage that creates an archive from a suspicious folder, either a system folder or one of the folders often used by attackers for staging purposes

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X__Junior (Nextron Systems), Florian Roth (Nextron Systems)Created Thu Dec 15Updated Tue Jan 02afe52666-401e-4a02-b4ff-5d128990b8cbwindows

Log Source

WindowsProcess Creation

ProductWindows← raw: windows

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

detection:
    # Example : rar.exe a -m5 -r -y -ta20210204000000 -hp1qazxcde32ws -v2560k Asia1Dpt-PC-c.rar c:\\*.doc c:\\*.docx c:\\*.xls c:\\*.xlsx c:\\*.pdf c:\\*.ppt c:\\*.pptx c:\\*.jpg c:\\*.txt >nul
    selection_opt_1:
        - Image|endswith: '\rar.exe'
        - Description: 'Command line RAR'
    selection_opt_2:
        CommandLine|contains:
            - '.exe a '
            - ' a -m'
    selection_cli_flags:
        CommandLine|contains|all:
            - ' -hp' # password
            - ' -r ' # recursive
    selection_cli_folders:
        CommandLine|contains:
            - ' ?:\\\*.'
            - ' ?:\\\\\*.'
            - ' ?:\$Recycle.bin\'
            - ' ?:\PerfLogs\'
            - ' ?:\Temp'
            - ' ?:\Users\Public\'
            - ' ?:\Windows\'
            - ' %public%'
    condition: 1 of selection_opt_* and all of selection_cli_*