Multiple Users Remotely Failing To Authenticate From Single Source

 1title: Multiple Users Remotely Failing To Authenticate From Single Source
 2id: add2ef8d-dc91-4002-9e7e-f2702369f53a
 3status: unsupported
 4description: Detects a source system failing to authenticate against a remote host with multiple users.
 5references:
 6    - https://docs.splunk.com/Documentation/ESSOC/3.22.0/stories/UseCase#Active_directory_password_spraying
 7author: Mauricio Velazco
 8date: 2021/06/01
 9modified: 2023/02/24
10tags:
11    - attack.t1110.003
12    - attack.initial_access
13    - attack.privilege_escalation
14logsource:
15    product: windows
16    service: security
17detection:
18    selection1:
19        EventID: 4625
20        LogonType: 3
21    filter:
22        IpAddress: '-'
23    timeframe: 24h
24    condition: selection1 and not filter | count(TargetUserName) by IpAddress > 10
25falsepositives:
26    - Terminal servers
27    - Jump servers
28    - Other multiuser systems like Citrix server farms
29    - Workstations with frequently changing users
30level: medium