Weak Encryption Enabled and Kerberoast

Detects scenario where weak encryption is enabled for a user profile which could be used for hash/password cracking.

Sigma rule (View on GitHub)

 1title: Weak Encryption Enabled and Kerberoast
 2id: f6de9536-0441-4b3f-a646-f4e00f300ffd
 3status: test
 4description: Detects scenario where weak encryption is enabled for a user profile which could be used for hash/password cracking.
 5references:
 6    - https://adsecurity.org/?p=2053
 7    - https://blog.harmj0y.net/redteaming/another-word-on-delegation/
 8author: '@neu5ron'
 9date: 2017/07/30
10modified: 2021/11/27
11tags:
12    - attack.defense_evasion
13    - attack.t1562.001
14logsource:
15    product: windows
16    service: security
17    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'
18detection:
19    selection:
20        EventID: 4738
21    # According to Microsoft, the bit values are listed here: https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4720
22    # However, that seems to be a simple copy from https://learn.microsoft.com/en-us/troubleshoot/windows-server/active-directory/useraccountcontrol-manipulate-account-properties
23    # and the actual flags that are used are quite different and, unfortunately, not documented.
24    # https://github.com/mdecrevoisier/EVTX-to-MITRE-Attack/ contains a number of EVTX files with relevant events, which can be used to extract
25    # the following values.
26    olduac_des: # 0x8000
27        OldUacValue|endswith:
28            - 8???
29            - 9???
30            - A???
31            - B???
32            - C???
33            - D???
34            - E???
35            - F???
36    newuac_des:
37        NewUacValue|endswith:
38            - 8???
39            - 9???
40            - A???
41            - B???
42            - C???
43            - D???
44            - E???
45            - F???
46    olduac_preauth: # 0x10000
47        OldUacValue|endswith:
48            - 1????
49            - 3????
50            - 5????
51            - 7????
52            - 9????
53            - B????
54            - D????
55            - F????
56    newuac_preauth:
57        NewUacValue|endswith:
58            - 1????
59            - 3????
60            - 5????
61            - 7????
62            - 9????
63            - B????
64            - D????
65            - F????
66    olduac_encrypted: # 0x800
67        OldUacValue|endswith:
68            - 8??
69            - 9??
70            - A??
71            - B??
72            - C??
73            - D??
74            - E??
75            - F??
76    newuac_encrypted:
77        NewUacValue|endswith:
78            - 8??
79            - 9??
80            - A??
81            - B??
82            - C??
83            - D??
84            - E??
85            - F??
86    condition: selection and ((newuac_des and not olduac_des) or (newuac_preauth and not olduac_preauth) or (newuac_encrypted and not olduac_encrypted))
87falsepositives:
88    - Unknown
89level: high

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