Detection: AWS SetDefaultPolicyVersion

Updated Date: 2024-05-16 ID: 2a9b80d3-6340-4345-11ad-212bf3d0dac4 Author: Bhavin Patel, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects when a user sets a default policy version in AWS. It leverages AWS CloudTrail logs to identify the SetDefaultPolicyVersion event from the IAM service. This activity is significant because attackers may exploit this technique for privilege escalation, especially if previous policy versions grant more extensive permissions than the current one. If confirmed malicious, this could allow an attacker to gain elevated access to AWS resources, potentially leading to unauthorized actions and data breaches.

1`cloudtrail` eventName=SetDefaultPolicyVersion eventSource = iam.amazonaws.com 
2| stats count min(_time) as firstTime max(_time) as lastTime values(requestParameters.policyArn) as policy_arn by src requestParameters.versionId eventName eventSource aws_account_id errorCode userAgent eventID awsRegion userIdentity.principalId user_arn 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `aws_setdefaultpolicyversion_filter`

Data Source

Name Platform Sourcetype Source Supported App
AWS CloudTrail SetDefaultPolicyVersion AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail' N/A

Macros Used

Name Value
cloudtrail sourcetype=aws:cloudtrail
aws_setdefaultpolicyversion_filter search *
aws_setdefaultpolicyversion_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1078.004 Cloud Accounts Defense Evasion
T1078 Valid Accounts Initial Access
KillChainPhase.DELIVERY
KillChainPhase.EXPLOITAITON
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.CIS_10
APT28
APT29
APT33
APT5
Ke3chang
LAPSUS$
APT18
APT28
APT29
APT33
APT39
APT41
Akira
Axiom
Carbanak
Chimera
Cinnamon Tempest
Dragonfly
FIN10
FIN4
FIN5
FIN6
FIN7
FIN8
Fox Kitten
GALLIUM
Ke3chang
LAPSUS$
Lazarus Group
Leviathan
OilRig
POLONIUM
PittyTiger
Sandworm Team
Silence
Silent Librarian
Suckfly
Threat Group-3390
Wizard Spider
menuPass

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

You must install splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs.

Known False Positives

While this search has no known false positives, it is possible that an AWS admin has legitimately set a default policy to allow a user to access all resources. That said, AWS strongly advises against granting full control to all AWS resources

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
From IP address $src$, user $user_arn$ has trigged an event $eventName$ for updating the the default policy version 30 50 60
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_cloudtrail aws:cloudtrail
Integration ✅ Passing Dataset aws_cloudtrail aws:cloudtrail

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: GitHub | Version: 2