This search looks for AssumeRole events where an IAM role in a different account is requested for the first time.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Authentication
- Last Updated: 2020-05-28
- Author: Rico Valdez, Splunk
- ID: 21193641-cb96-4a2c-a707-d9b9a7f7792b
Kill Chain Phase
- Actions on Objectives
- CIS 16
1 2 3 4 5 6 7 8 9 10 11 12 | tstats min(_time) as firstTime max(_time) as lastTime from datamodel=Authentication where Authentication.signature=AssumeRole by Authentication.vendor_account Authentication.user Authentication.src Authentication.user_role | `drop_dm_object_name(Authentication)` | rex field=user_role "arn:aws:sts:*:(?<dest_account>.*):" | where vendor_account != dest_account | rename vendor_account as requestingAccountId dest_account as requestedAccountId | lookup previously_seen_aws_cross_account_activity requestingAccountId, requestedAccountId, OUTPUTNEW firstTime | eval status = if(firstTime > relative_time(now(), "-24h@h"),"New Cross Account Activity","Previously Seen") | where status = "New Cross Account Activity" | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `aws_cross_account_activity_from_previously_unseen_account_filter`
The SPL above uses the following Macros:
aws_cross_account_activity_from_previously_unseen_account_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
The SPL above uses the following Lookups:
How To Implement
You must be ingesting your cloud infrastructure logs from your cloud provider. You should run the baseline search
Previously Seen AWS Cross Account Activity - Initial to build the initial table of source IP address, geographic locations, and times. You must also enable the second baseline search
Previously Seen AWS Cross Account Activity - Update to keep this table up to date and to age out old data. You can also provide additional filtering for this search by customizing the
Known False Positives
Using multiple AWS accounts and roles is perfectly valid behavior. It’s suspicious when an account requests privileges of an account it hasn’t before. You should validate with the account owner that this is a legitimate request.
Associated Analytic story
|15.0||30||50||AWS account $requestingAccountId$ is trying to access resource from some other account $requestedAccountId$, for the first time.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1