Sigma rule: Suspicious Environment Variable Has Been Registered

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-97d71263e676, updated 2023-08-17T00:00:00.000Z.

Rule

Title
Suspicious Environment Variable Has Been Registered
Status
test
Level
high
Author
Nasreddine Bencherchali (Nextron Systems)
Date
2022-12-20
Modified
2023-08-17
File
rules/windows/registry/registry_set/registry_set_suspicious_env_variables.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the creation of user-specific or system-wide environment variables via the registry. Which contains suspicious commands and strings

Log source

product
windows
category
registry_set

Detection

selection_main:
    TargetObject|contains: '\Environment\'
selection_details:
    - Details:
          - 'powershell'
          - 'pwsh'
    - Details|contains:
          # Add more suspicious strings in env variables below
          - '\AppData\Local\Temp\'
          - 'C:\Users\Public\'
          # Base64 MZ Header
          - 'TVqQAAMAAAAEAAAA' # MZ..........
          - 'TVpQAAIAAAAEAA8A'
          - 'TVqAAAEAAAAEABAA'
          - 'TVoAAAAAAAAAAAAA'
          - 'TVpTAQEAAAAEAAAA'
          # Base64 Invoke- (UTF-8)
          - 'SW52b2tlL'
          - 'ludm9rZS'
          - 'JbnZva2Ut'
          # Base64 Invoke- (UTF-16LE)
          - 'SQBuAHYAbwBrAGUALQ'
          - 'kAbgB2AG8AawBlAC0A'
          - 'JAG4AdgBvAGsAZQAtA'
    - Details|startswith:  # https://gist.github.com/Neo23x0/6af876ee72b51676c82a2db8d2cd3639
          - 'SUVY'
          - 'SQBFAF'
          - 'SQBuAH'
          - 'cwBhA'
          - 'aWV4'
          - 'aQBlA'
          - 'R2V0'
          - 'dmFy'
          - 'dgBhA'
          - 'dXNpbm'
          - 'H4sIA'
          - 'Y21k'
          - 'cABhAH'
          - 'Qzpc'
          - 'Yzpc'
condition: all of selection_*

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.persistence
  • attack.stealth

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/registry/registry_set/registry_set_suspicious_env_variables.yml

Sources and licences

  • SigmaHQ

    "Suspicious Environment Variable Has Been Registered" by Nasreddine Bencherchali (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/registry/registry_set/registry_set_suspicious_env_variables.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: Suspicious Environment Variable Has Been Registered",
entity page, dataset version ref-97d71263e676, updated 2023-08-17T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/966315ef-c5e1-4767-ba25-fce9c8de3660 (accessed 2026-11-03).
Underlying source: SigmaHQ rule 966315ef-c5e1-4767-ba25-fce9c8de3660, 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.