Name:AWS Detect Users with KMS keys performing encryption S3 id:884a5f59-eec7-4f4a-948b-dbde18225fdc version:4 date:2024-09-30 author:Rod Soto, Patrick Bareiss Splunk status:production type:Anomaly Description:The following analytic identifies users with KMS keys performing encryption operations on S3 buckets. It leverages AWS CloudTrail logs to detect the `CopyObject` event where server-side encryption with AWS KMS is specified. This activity is significant as it may indicate unauthorized or suspicious encryption of data, potentially masking exfiltration or tampering efforts. If confirmed malicious, an attacker could be encrypting sensitive data to evade detection or preparing it for exfiltration, posing a significant risk to data integrity and confidentiality. Data_source:
-AWS CloudTrail
search:`cloudtrail` eventName=CopyObject requestParameters.x-amz-server-side-encryption="aws:kms" | rename requestParameters.bucketName AS bucketName, requestParameters.x-amz-copy-source AS src_file, requestParameters.key AS dest_file | stats count min(_time) as firstTime max(_time) as lastTime values(bucketName) as bucketName values(src_file) AS src_file values(dest_file) AS dest_file values(userAgent) AS userAgent values(region) AS region values(src) AS src by user | `security_content_ctime(firstTime)`| `security_content_ctime(lastTime)` |`aws_detect_users_with_kms_keys_performing_encryption_s3_filter`
how_to_implement:You must install Splunk AWS add on and Splunk App for AWS. This search works with AWS CloudTrail logs known_false_positives:There maybe buckets provisioned with S3 encryption References: -https://rhinosecuritylabs.com/aws/s3-ransomware-part-1-attack-vector/ -https://github.com/d1vious/git-wild-hunt -https://www.youtube.com/watch?v=PgzNib37g0M drilldown_searches: name:'View the detection results for - "$user$"' search:'%original_detection_search% | search user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Ransomware Cloud' asset_type:S3 Bucket confidence:50 impact:30 message:User $user$ with KMS keys is performing encryption, against S3 buckets on these files $dest_file$ mitre_attack_id: - 'T1486' observable: name:'user' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'eventName' - 'requestParameters.x-amz-server-side-encryption' - 'requestParameters.bucketName' - 'requestParameters.x-amz-copy-source' - 'requestParameters.key' - 'userAgent' - 'region' risk_score:15 security_domain:threat
