Failed Logon From Public IP

Detects a failed logon attempt from a public IP. A login from a public IP can indicate a misconfigured firewall or network boundary.

Sigma rule (View on GitHub)

 1title: Failed Logon From Public IP
 2id: f88e112a-21aa-44bd-9b01-6ee2a2bbbed1
 3status: test
 4description: Detects a failed logon attempt from a public IP. A login from a public IP can indicate a misconfigured firewall or network boundary.
 5references:
 6    - https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4625
 7author: NVISO
 8date: 2020/05/06
 9modified: 2023/01/11
10tags:
11    - attack.initial_access
12    - attack.persistence
13    - attack.t1078
14    - attack.t1190
15    - attack.t1133
16logsource:
17    product: windows
18    service: security
19detection:
20    selection:
21        EventID: 4625
22    filter_main_ip_unknown:
23        IpAddress|contains: '-'
24    filter_main_ip_privatev4:
25        IpAddress|startswith:
26            - '10.' # 10.0.0.0/8
27            - '192.168.' # 192.168.0.0/16
28            - '172.16.' # 172.16.0.0/12
29            - '172.17.'
30            - '172.18.'
31            - '172.19.'
32            - '172.20.'
33            - '172.21.'
34            - '172.22.'
35            - '172.23.'
36            - '172.24.'
37            - '172.25.'
38            - '172.26.'
39            - '172.27.'
40            - '172.28.'
41            - '172.29.'
42            - '172.30.'
43            - '172.31.'
44            - '127.' # 127.0.0.0/8
45            - '169.254.' # 169.254.0.0/16
46    filter_main_ip_privatev6:
47        - IpAddress: '::1' # loopback
48        - IpAddress|startswith:
49              - 'fe80::' # link-local
50              - 'fc00::' # unique local
51    condition: selection and not 1 of filter_main_*
52falsepositives:
53    - Legitimate logon attempts over the internet
54    - IPv4-to-IPv6 mapped IPs
55level: medium

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