it is possible that a user downloaded these files to use them locally and there are aws services in configured that perform these activities for a legitimate reason. filter is needed.

Techniques

T1119

Sample rules

AWS Exfiltration via Anomalous GetObject API Activity

source: splunk
technicques:
- T1119

Description

The following analytic identifies anomalous GetObject API activity in AWS, indicating potential data exfiltration attempts. It leverages AWS CloudTrail logs and uses the anomalydetection command to detect unusual patterns in the frequency of GetObject API calls by analyzing fields such as “count,” “user_type,” and “user_arn” within a 10-minute window. This activity is significant as it may indicate unauthorized data access or exfiltration from S3 buckets. If confirmed malicious, attackers could exfiltrate sensitive data, leading to data breaches and compliance violations.

Detection logic

`cloudtrail` eventName=GetObject 
| bin _time span=10m 
|  stats count values(requestParameters.bucketName) as bucketName by _time src_ip aws_account_id user_type user_arn userIdentity.principalId 
| anomalydetection "count" "user_type" "user_arn" action=annotate 
| search probable_cause=* 
|`aws_exfiltration_via_anomalous_getobject_api_activity_filter`