Sigma rule: Abusing Findstr for Defense Evasion

Rule

Title

Abusing Findstr for Defense Evasion

Status

deprecated

Level

medium

Author

Furkan CALISKAN, @caliskanfurkan_, @oscd_initiative, Nasreddine Bencherchali

Date

2020/10/05

Modified

2022/10/12

File

deprecated/windows/proc_creation_win_lolbin_findstr.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Attackers can use findstr to hide their artifacts or search specific strings and evade defense mechanism

Log source

product

windows

category

process_creation

Detection

selection_findstr:
    - CommandLine|contains: findstr
    - Image|endswith: 'findstr.exe'
    - OriginalFileName: 'FINDSTR.EXE'
selection_cli_download_1:
    CommandLine|contains:
        - ' /v '
        - ' -v '
selection_cli_download_2:
    CommandLine|contains:
        - ' /l '
        - ' -l '
selection_cli_creds_1:
    CommandLine|contains:
        - ' /s '
        - ' -s '
selection_cli_creds_2:
    CommandLine|contains:
        - ' /i '
        - ' -i '
condition: selection_findstr and (all of selection_cli_download* or all of selection_cli_creds*)

False positives (as the rule lists them)

• Administrative findstr usage

Tags

• attack.defense_evasion
• attack.t1218
• attack.t1564.004
• attack.t1552.001
• attack.t1105

MITRE ATT&CK ids this rule names

• T1105
• T1218
• T1552.001
• T1564.004

References

• https://lolbas-project.github.io/lolbas/Binaries/Findstr/
• https://oddvar.moe/2018/04/11/putting-data-in-alternate-data-streams-and-how-to-execute-it-part-2/
• https://gist.github.com/api0cradle/cdd2d0d0ec9abb686f0e89306e277b8f

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