Detection: AWS Defense Evasion Impair Security Services

Updated Date: 2024-10-17 ID: b28c4957-96a6-47e0-a965-6c767aac1458 Author: Bhavin Patel, Gowthamaraj Rajendran, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects attempts to delete critical AWS security service configurations, such as CloudWatch alarms, GuardDuty detectors, and Web Application Firewall rules. It leverages CloudTrail logs to identify specific API calls like "DeleteLogStream" and "DeleteDetector." This activity is significant because it indicates potential efforts to disable security monitoring and evade detection. If confirmed malicious, this could allow attackers to operate undetected, escalate privileges, or exfiltrate data without triggering security alerts, severely compromising the security posture of the AWS environment.

Search

1`cloudtrail` eventName IN ("DeleteLogStream","DeleteDetector","DeleteIPSet","DeleteWebACL","DeleteRule","DeleteRuleGroup","DeleteLoggingConfiguration","DeleteAlarms") 
2| stats count min(_time) as firstTime max(_time) as lastTime values(eventName)  as eventName values(eventSource) as eventSource values(requestParameters.*) as * by src region user_arn aws_account_id user_type user_agent errorCode
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)`
5|  `aws_defense_evasion_impair_security_services_filter`

Data Source

Name	Platform	Sourcetype	Source
AWS CloudTrail DeleteAlarms	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail DeleteDetector	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail DeleteIPSet	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail DeleteLogStream	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail DeleteRule	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail DeleteWebACL	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`

Macros Used

Name	Value
cloudtrail	`sourcetype=aws:cloudtrail`
aws_defense_evasion_impair_security_services_filter	`search *`

aws_defense_evasion_impair_security_services_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
T1562.008	Disable or Modify Cloud Logs	Defense Evasion
T1562	Impair Defenses	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

APT29

Magic Hound

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 Risk Event	False

This configuration file applies to all detections of type hunting.

Implementation

You must install Splunk AWS Add on and enable CloudTrail logs in your AWS Environment.

Known False Positives

While this search has no known false positives, it is possible that it is a legitimate admin activity. Please consider filtering out these noisy events using userAgent, user_arn field names.

Associated Analytic Story

AWS Defense Evasion

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
User $user_arn$ has made potentially risky api calls $eventName$ that could impair AWS security services for account id $aws_account_id$	42	70	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: 3