Invalid Users Failing To Authenticate From Single Source Using NTLM

 1title: Invalid Users Failing To Authenticate From Single Source Using NTLM
 2id: 56d62ef8-3462-4890-9859-7b41e541f8d5
 3status: unsupported
 4description: Detects failed logins with multiple invalid domain accounts from a single source system using the NTLM protocol.
 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: 2023/03/13
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: 4776
20        Status: '*0xC0000064' # The username you typed does not exist. Bad username.
21    filter:
22        TargetUserName: '*$'
23    timeframe: 24h
24    condition: selection1 and not filter | count(TargetUserName) by Workstation > 10
25falsepositives:
26    - Terminal servers
27    - Jump servers
28    - Other multiuser systems like Citrix server farms
29    - Workstations with frequently changing users
30level: medium