Windows Security: Account Encryption/Preauth/Delegation Flags Weakened in User Account Changes

Flags Windows Event ID 4738 user account changes that enable weaker encryption or related pre-auth behavior.

FreeReviewedSigma · High · v2

Product: windows
Service: security
Author: @neu5ron (SigmaHQ), DRL 1.1
Published: 2017-07-30
Updated: 2026-07-31

ATT&CK techniques

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows Security Event ID 4738 where a user account is modified to enable weaker cryptographic-related settings by changing specific UserAccountControl flag patterns for DES, preauthentication-related behavior, or encryption. Such changes can facilitate offline password/hash cracking by weakening how Kerberos-related protections behave for that account. It relies on audit telemetry from Event ID 4738 and matches transitions from prior flag patterns to new flag patterns using suffix-based value conditions.

Reporting behind it

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Windows Security: Account Encryption/Preauth/Delegation Flags Weakened in User Account Changes

Pivot detection · T1685 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-security-4738-kerberoast-risk-via-weak-encryption-enabled-uac-change-f6de9536

title: "Windows Security: Account Encryption/Preauth/Delegation Flags Weakened in User Account Changes"
id: d27fecb6-80d0-4d44-a8cb-e23f178e4198
status: test
description: This rule flags Windows Security Event ID 4738 where a user account is modified to enable weaker cryptographic-related settings by changing specific UserAccountControl flag patterns for DES, preauthentication-related behavior, or encryption. Such changes can facilitate offline password/hash cracking by weakening how Kerberos-related protections behave for that account. It relies on audit telemetry from Event ID 4738 and matches transitions from prior flag patterns to new flag patterns using suffix-based value conditions.
references:
  - https://adsecurity.org/?p=2053
  - https://blog.harmj0y.net/redteaming/another-word-on-delegation/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/builtin/security/win_security_alert_enable_weak_encryption.yml
author: "@neu5ron, Huntrule Team"
date: 2017-07-30
modified: 2021-11-27
tags:
  - attack.defense-impairment
  - attack.t1685
logsource:
  product: windows
  service: security
  definition: "Requirements: Audit Policy : Account Management > Audit User Account Management, Group Policy : Computer Configuration\\Windows Settings\\Security Settings\\Advanced Audit Policy Configuration\\Audit Policies\\Account Management\\Audit User Account Management"
detection:
  selection:
    EventID: 4738
  olduac_des:
    OldUacValue|endswith:
      - 8???
      - 9???
      - A???
      - B???
      - C???
      - D???
      - E???
      - F???
  newuac_des:
    NewUacValue|endswith:
      - 8???
      - 9???
      - A???
      - B???
      - C???
      - D???
      - E???
      - F???
  olduac_preauth:
    OldUacValue|endswith:
      - 1????
      - 3????
      - 5????
      - 7????
      - 9????
      - B????
      - D????
      - F????
  newuac_preauth:
    NewUacValue|endswith:
      - 1????
      - 3????
      - 5????
      - 7????
      - 9????
      - B????
      - D????
      - F????
  olduac_encrypted:
    OldUacValue|endswith:
      - 8??
      - 9??
      - A??
      - B??
      - C??
      - D??
      - E??
      - F??
  newuac_encrypted:
    NewUacValue|endswith:
      - 8??
      - 9??
      - A??
      - B??
      - C??
      - D??
      - E??
      - F??
  condition: selection and ((newuac_des and not olduac_des) or (newuac_preauth and not olduac_preauth) or (newuac_encrypted and not olduac_encrypted))
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: f6de9536-0441-4b3f-a646-f4e00f300ffd
    type: derived

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