Try in Splunk Security Cloud

Description

This search looks for cloud instances being modified by users who have not previously modified them.

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
  • ID.AM
CIS20
  • CIS 1
CVE
1
2
3
4
5
6
7
8
9
10
11
| tstats `security_content_summariesonly` count earliest(_time) as firstTime, latest(_time) as lastTime values(All_Changes.object_id) as object_id values(All_Changes.command) as command from datamodel=Change where All_Changes.action=modified All_Changes.change_type=EC2 All_Changes.status=success by All_Changes.user 
| `drop_dm_object_name("All_Changes")` 
| lookup previously_seen_cloud_instance_modifications_by_user user as user OUTPUTNEW firstTimeSeen, enough_data 
| eventstats max(enough_data) as enough_data 
| where enough_data=1 
| eval firstTimeSeenUser=min(firstTimeSeen) 
| where isnull(firstTimeSeenUser) OR firstTimeSeenUser > relative_time(now(), "-24h@h") 
| table firstTime user command object_id count 
| `security_content_ctime(firstTime)` 
| `cloud_instance_modified_by_previously_unseen_user_filter`

Macros

The SPL above uses the following Macros:

Note that cloud_instance_modified_by_previously_unseen_user_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
  • All_Changes.object_id
  • All_Changes.command
  • All_Changes.action
  • All_Changes.change_type
  • All_Changes.status
  • All_Changes.user

How To Implement

This search has a dependency on other searches to create and update a baseline of users observed to be associated with this activity. The search “Previously Seen Cloud Instance Modifications By User - Update” should be enabled for this detection to properly work.

Known False Positives

It’s possible that a new user will start to modify EC2 instances when they haven’t before for any number of reasons. Verify with the user that is modifying instances that this is the intended behavior.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
42.0 70 60 User $user$ is modifying an instance $dest$ for the first time.

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