Sigma rule: Suspicious Greedy Compression Using Rar.EXE

Rule

Title

Suspicious Greedy Compression Using Rar.EXE

Status

test

Level

high

Author

X__Junior (Nextron Systems), Florian Roth (Nextron Systems)

Date

2022-12-15

Modified

2024-01-02

File

rules/windows/process_creation/proc_creation_win_rar_susp_greedy_compression.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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

Log source

product

windows

category

process_creation

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_*

False positives (as the rule lists them)

• Unknown

Tags

• attack.execution
• attack.t1059

MITRE ATT&CK ids this rule names

• T1059

References

• https://decoded.avast.io/martinchlumecky/png-steganography

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_rar_susp_greedy_compression.yml