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Description

This search detects new API calls that have either never been seen before or that have not been seen in the previous hour, where the identity type is AssumedRole.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2018-04-16
  • Author: Bhavin Patel, Splunk
  • ID: 22773e84-bac0-4595-b086-20d3f335b4f1

Annotations

ATT&CK
ID Technique Tactic
T1078.004 Cloud Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
  • ID.AM
CIS20
  • CIS 1
CVE
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`cloudtrail` eventType=AwsApiCall errorCode=success userIdentity.type=AssumedRole [search `cloudtrail` eventType=AwsApiCall errorCode=success  userIdentity.type=AssumedRole 
| stats earliest(_time) as earliest latest(_time) as latest by userName eventName 
|  inputlookup append=t previously_seen_api_calls_from_user_roles 
| stats min(earliest) as earliest, max(latest) as latest by userName eventName 
| outputlookup previously_seen_api_calls_from_user_roles
| eval newApiCallfromUserRole=if(earliest>=relative_time(now(), "-70m@m"), 1, 0) 
| where newApiCallfromUserRole=1 
| `security_content_ctime(earliest)` 
| `security_content_ctime(latest)` 
| table eventName userName]  
|rename userName as user
| stats values(eventName) earliest(_time) as earliest latest(_time) as latest by user 
| `security_content_ctime(earliest)` 
| `security_content_ctime(latest)` 
| `detect_new_api_calls_from_user_roles_filter`

Macros

The SPL above uses the following Macros:

Note that detect_new_api_calls_from_user_roles_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Lookups

The SPL above uses the following Lookups:

Required field

  • _time
  • eventType
  • errorCode
  • userIdentity.type
  • userName
  • eventName

How To Implement

You must install the AWS App for Splunk (version 5.1.0 or later) and Splunk Add-on for AWS (version 4.4.0 or later), then configure your AWS CloudTrail inputs. This search works best when you run the “Previously seen API call per user roles in AWS CloudTrail” support search once to create a history of previously seen user roles.

Known False Positives

It is possible that there are legitimate user roles making new or infrequently used API calls in your infrastructure, causing the search to trigger.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
25.0 50 50 tbd

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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