Sigma rule: ProxyLogon MSExchange OabVirtualDirectory

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-824665870a8e, updated 2023-01-23T00:00:00.000Z.

Rule

Title
ProxyLogon MSExchange OabVirtualDirectory
Status
test
Level
critical
Author
Florian Roth (Nextron Systems)
Date
2021-08-09
Modified
2023-01-23
File
rules/windows/builtin/msexchange/win_exchange_proxylogon_oabvirtualdir.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects specific patterns found after a successful ProxyLogon exploitation in relation to a Commandlet invocation of Set-OabVirtualDirectory

Log source

product
windows
service
msexchange-management

Detection

keywords_cmdlet:
    '|all':
        - 'OabVirtualDirectory'
        - ' -ExternalUrl '
keywords_params:
    - 'eval(request'
    - 'http://f/<script'
    - '"unsafe"};'
    - 'function Page_Load()'
condition: keywords_cmdlet and keywords_params

False positives (as the rule lists them)

  • Unlikely

Tags

  • attack.t1587.001
  • attack.resource-development

MITRE ATT&CK ids this rule names

References

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/builtin/msexchange/win_exchange_proxylogon_oabvirtualdir.yml

Sources and licences

  • SigmaHQ

    "ProxyLogon MSExchange OabVirtualDirectory" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/builtin/msexchange/win_exchange_proxylogon_oabvirtualdir.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: ProxyLogon MSExchange OabVirtualDirectory",
entity page, dataset version ref-824665870a8e, updated 2023-01-23T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/550d3350-bb8a-4ff3-9533-2ba533f4a1c0 (accessed 2026-11-03).
Underlying source: SigmaHQ rule 550d3350-bb8a-4ff3-9533-2ba533f4a1c0, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.