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Description

This search will detect a spike in the number of API calls made to your cloud infrastructure environment about security groups by a user.

Annotations

ATT&CK
ID Technique Tactic
T1078.004 Cloud Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
T1078 Valid Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
Kill Chain Phase
  • Actions on Objectives
NIST
  • DE.DP
  • DE.CM
  • PR.AC
CIS20
  • CIS 16
CVE
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| tstats count as security_group_api_calls values(All_Changes.command) as command from datamodel=Change where All_Changes.object_category=firewall AND All_Changes.status=success by All_Changes.user _time span=1h 
| `drop_dm_object_name("All_Changes")` 
| eval HourOfDay=strftime(_time, "%H") 
| eval HourOfDay=floor(HourOfDay/4)*4 
| eval DayOfWeek=strftime(_time, "%w") 
| eval isWeekend=if(DayOfWeek >= 1 AND DayOfWeek <= 5, 0, 1) 
| join user HourOfDay isWeekend [ summary cloud_excessive_security_group_api_calls_v1] 
| where cardinality >=16 
| apply cloud_excessive_security_group_api_calls_v1 threshold=0.005 
| rename "IsOutlier(security_group_api_calls)" as isOutlier 
| where isOutlier=1 
| eval expected_upper_threshold = mvindex(split(mvindex(BoundaryRanges, -1), ":"), 0) 
| where security_group_api_calls > expected_upper_threshold 
| eval distance_from_threshold = security_group_api_calls - expected_upper_threshold 
| table _time, user, command, security_group_api_calls, expected_upper_threshold, distance_from_threshold 
| `abnormally_high_number_of_cloud_security_group_api_calls_filter`

Macros

The SPL above uses the following Macros:

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

Required field

  • _time
  • All_Changes.command
  • All_Changes.object_category
  • All_Changes.status
  • All_Changes.user

How To Implement

You must be ingesting your cloud infrastructure logs. You also must run the baseline search Baseline Of Cloud Security Group API Calls Per User to create the probability density function model.

Known False Positives

Associated Analytic story

RBA

Risk Score Impact Confidence Message
15.0 30 50 user $user$ has made $api_calls$ api calls related to security groups, violating the dynamic threshold of $expected_upper_threshold$ with the following command $command$.

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

source | version: 1