assumerole may be done by a system or network administrator. verify whether the user identity, user agent, and/or hostname should be making changes in your environment.

source: <a href=https://github.com/SigmaHQ/sigma/blob/master/rules/cloud/aws/cloudtrail/aws_sts_assumerole_misuse.yml>sigma
technicques: t1548 t1550 t1550.001

Techniques

Identifies the suspicious use of AssumeRole. Attackers could move laterally and escalate privileges.

condition: selection
selection:
  userIdentity.sessionContext.sessionIssuer.type: Role
  userIdentity.type: AssumedRole