Detection: AWS Detect Users creating keys with encrypt policy without MFA

Updated Date: 2024-09-30 ID: c79c164f-4b21-4847-98f9-cf6a9f49179e Author: Rod Soto, Patrick Bareiss Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of AWS KMS keys with an encryption policy accessible to everyone, including external entities. It leverages AWS CloudTrail logs to identify CreateKey or PutKeyPolicy events where the kms:Encrypt action is granted to all principals. This activity is significant as it may indicate a compromised account, allowing an attacker to misuse the encryption key to target other organizations. If confirmed malicious, this could lead to unauthorized data encryption, potentially disrupting operations and compromising sensitive information across multiple entities.

Search

 1`cloudtrail` eventName=CreateKey OR eventName=PutKeyPolicy 
 2| spath input=requestParameters.policy output=key_policy_statements path=Statement{} 
 3| mvexpand key_policy_statements 
 4| spath input=key_policy_statements output=key_policy_action_1 path=Action 
 5| spath input=key_policy_statements output=key_policy_action_2 path=Action{} 
 6| eval key_policy_action=mvappend(key_policy_action_1, key_policy_action_2) 
 7| spath input=key_policy_statements output=key_policy_principal path=Principal.AWS 
 8| search key_policy_action="kms:Encrypt" AND key_policy_principal="*" 
 9| stats count min(_time) as firstTime max(_time) as lastTime by eventName eventSource eventID awsRegion userIdentity.principalId user 
10| `security_content_ctime(firstTime)`
11| `security_content_ctime(lastTime)` 
12|`aws_detect_users_creating_keys_with_encrypt_policy_without_mfa_filter`

Data Source

Name	Platform	Sourcetype	Source
AWS CloudTrail CreateKey	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`
AWS CloudTrail PutKeyPolicy	AWS	`'aws:cloudtrail'`	`'aws_cloudtrail'`

Macros Used

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

aws_detect_users_creating_keys_with_encrypt_policy_without_mfa_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
T1486	Data Encrypted for Impact	Impact

KillChainPhase.ACTIONS_ON_OBJECTIVES

NistCategory.DE_CM

Cis18Value.CIS_10

APT38

APT41

Akira

FIN7

FIN8

INC Ransom

Indrik Spider

Magic Hound

Moonstone Sleet

Sandworm Team

Scattered Spider

TA505

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

unknown

Associated Analytic Story

Ransomware Cloud

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
AWS account is potentially compromised and user $user$ is trying to compromise other accounts.	25	50	50

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