unusual_number_of_remote_endpoint_authentication_events.yml

name: Unusual Number of Remote Endpoint Authentication Events
id: acb5dc74-5324-11ec-a36d-acde48001122
version: 1
date: '2021-12-01'
author: Mauricio Velazco, Splunk
status: experimental
type: Hunting
description: 'The following hunting analytic leverages Event ID 4624, `An account
  was successfully logged on`, to identify an unusual number of remote authentication
  attempts coming from one source. An endpoint authenticating to a large number of
  remote endpoints could represent malicious behavior like lateral movement, malware
  staging, reconnaissance, etc. The detection calculates the standard deviation for each host and leverages the 3-sigma statistical rule to identify an unusual high number of authentication events.To customize this analytic, users can try different combinations of the `bucket` span time,  the calculation of the `upperBound` field as well as the Outlier calculation.This logic can be used for real time security monitoring as well as threat hunting exercises.'
data_source:
- Windows Event Log Security 4624
search: ' `wineventlog_security` EventCode=4624 Logon_Type=3 Account_Name!="*$" |
  eval Source_Account = mvindex(Account_Name, 1) | bucket span=2m _time | stats dc(ComputerName)
  AS unique_targets values(ComputerName) as target_hosts by _time, Source_Network_Address,
  Source_Account | eventstats avg(unique_targets) as comp_avg , stdev(unique_targets)
  as comp_std by Source_Network_Address, Source_Account | eval upperBound=(comp_avg+comp_std*3)
  | eval isOutlier=if(unique_targets >10 and unique_targets >= upperBound, 1, 0) |
  `unusual_number_of_remote_endpoint_authentication_events_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting
  Windows Event Logs from domain controllers as well as member servers and workstations.
  The Advanced Security Audit policy setting `Audit Logon` within `Logon/Logoff` needs
  to be enabled.
known_false_positives: An single endpoint authenticating to a large number of hosts
  is not common behavior. Possible false positive scenarios include but are not limited
  to vulnerability scanners, jump servers and missconfigured systems.
references:
- https://attack.mitre.org/techniques/T1078/
tags:
  analytic_story:
  - Active Directory Lateral Movement
  - Active Directory Privilege Escalation
  asset_type: Endpoint
  confidence: 60
  impact: 70
  message: Unusual number of remote authentication events from $Source_Network_Address$
  mitre_attack_id:
  - T1078
  observable:
  - name: target_hosts
    type: Endpoint
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - EventCode
  - Logon_Type
  - Caller_Process_Name
  - Security_ID
  - Account_Name
  - ComputerName
  risk_score: 42
  security_domain: endpoint