Sigma rule: Exchange ProxyShell Pattern

Rule

Title

Exchange ProxyShell Pattern

Status

test

Level

high

Author

Florian Roth (Nextron Systems), Rich Warren

Date

2021-08-07

Modified

2023-01-02

File

rules-emerging-threats/2021/Exploits/ProxyShell-Exploit/web_exchange_proxyshell.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects URL patterns that could be found in ProxyShell exploitation attempts against Exchange servers (failed and successful)

Log source

category

webserver

Detection

selection_1:
    sc-status: 401
selection_1_auto:
    cs-uri-query|contains: '/autodiscover.json'
selection_1_uri:
    cs-uri-query|contains:
        - '/powershell'
        - '/mapi/nspi'
        - '/EWS'
        - 'X-Rps-CAT'
selection_poc:
    sc-status: 401
    cs-uri-query|contains:
        # since we don't know how it will appear in the log files, we'll just use all versions
        - 'autodiscover.json?@'
        - 'autodiscover.json%3f@'
        - '%[email protected]'
        - 'Email=autodiscover/autodiscover.json'
        - '[email protected]'
condition: all of selection_1* or selection_poc

False positives (as the rule lists them)

• Unknown

Tags

• attack.initial-access
• attack.t1190
• detection.emerging-threats

MITRE ATT&CK ids this rule names

• T1190

References

• https://youtu.be/5mqid-7zp8k?t=2231
• https://blog.orange.tw/2021/08/proxylogon-a-new-attack-surface-on-ms-exchange-part-1.html
• https://peterjson.medium.com/reproducing-the-proxyshell-pwn2own-exploit-49743a4ea9a1

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/ProxyShell-Exploit/web_exchange_proxyshell.yml