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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.\

  • Type: Hunting
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-12-01
  • Author: Mauricio Velazco, Splunk
  • ID: acb5dc74-5324-11ec-a36d-acde48001122

ATT&CK

ID Technique Tactic
T1078 Valid Accounts Defense Evasion, Persistence, Privilege Escalation, Initial Access
 `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`

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting Windows Event Logs from domain controllers aas well as member servers and workstations. The Advanced Security Audit policy setting Audit Logon within Logon/Logoff needs to be enabled.

Required field

  • _time
  • EventCode
  • Logon_Type
  • Caller_Process_Name
  • Security_ID
  • Account_Name
  • ComputerName

Kill Chain Phase

  • Reconnaissance
  • Lateral Movement

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.

RBA

Risk Score Impact Confidence Message
42.0 70 60 None

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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