Sigma rule: Suspicious PowerShell Download and Execute Pattern

Rule

Title

Suspicious PowerShell Download and Execute Pattern

Status

test

Level

high

Author

Florian Roth (Nextron Systems)

Date

2022-02-28

Modified

2022-03-01

File

rules/windows/process_creation/proc_creation_win_powershell_susp_download_patterns.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects suspicious PowerShell download patterns that are often used in malicious scripts, stagers or downloaders (make sure that your backend applies the strings case-insensitive)

Log source

product

windows

category

process_creation

Detection

selection:
    CommandLine|contains: # make sure that your backend applies the strings case-insensitive
        - 'IEX ((New-Object Net.WebClient).DownloadString'
        - 'IEX (New-Object Net.WebClient).DownloadString'
        - 'IEX((New-Object Net.WebClient).DownloadString'
        - 'IEX(New-Object Net.WebClient).DownloadString'
        - ' -command (New-Object System.Net.WebClient).DownloadFile('
        - ' -c (New-Object System.Net.WebClient).DownloadFile('
condition: selection

False positives (as the rule lists them)

• Software installers that pull packages from remote systems and execute them

Tags

• attack.execution
• attack.t1059.001

MITRE ATT&CK ids this rule names

• T1059.001

Related rules

• 3b6ab547-8ec2-4991-b9d2-2b06702a48d7 (derived)

References

• https://gist.github.com/jivoi/c354eaaf3019352ce32522f916c03d70
• https://www.trendmicro.com/en_us/research/22/j/lv-ransomware-exploits-proxyshell-in-attack.html

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_powershell_susp_download_patterns.yml