A machine learning job detected activity for a username that is not normally active, which can indicate unauthorized changes, activity by unauthorized users, lateral movement, or compromised credentials. In many organizations, new usernames are not often created apart from specific types of system activities, such as creating new accounts for new employees. These user accounts quickly become active and routine. Events from rarely used usernames can point to suspicious activity. Unusual usernames can also indicate pivoting, where compromised credentials are used to try and move laterally from one host to another.
Rule type: machine_learning
Machine learning job: windows_anomalous_user_name_ecs
Machine learning anomaly threshold: 50
Risk score: 21
Runs every: 15 minutes
Maximum alerts per execution: 100
- Threat Detection
Version: 3 (version history)
Added (Elastic Stack release): 7.7.0
Last modified (Elastic Stack release): 7.10.0
Rule authors: Elastic
Rule license: Elastic License
Uncommon user activity can be due to an administrator or help desk technician logging onto a workstation or server in order to perform manual troubleshooting or reconfiguration.
Alerts from this rule indicate activity for a Windows user name that is rare and unusual. Here are some possible avenues of investigation:
- Consider the user as identified by the username field. Is this program part of an expected workflow for the user who ran this program on this host? Could this be related to occasional troubleshooting or support activity?
- Examine the history of user activity. If this user manifested only very recently, it might be a service account for a new software package. If it has a consistent schedule - for example if it runs monthly or quarterly - it might be part of a monthly or quarterly business process.
- Examine the process arguments, title and working directory. These may provide indications as to the source of the program or the nature of the tasks that the user is performing.
- Consider the same for the parent process. If the parent process is a legitimate system utility or service, this could be related to software updates or system management. If the parent process is something user-facing like an Office application, this process could be more suspicious.
- Version 3 (7.10.0 release)
- Formatting only
- Version 2 (7.9.0 release)
- Formatting only