initial_access_ml_linux_anomalous_user_name.toml

[metadata]
creation_date = "2020/03/25"
maturity = "production"
updated_date = "2023/03/06"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"

[rule]
anomaly_threshold = 50
author = ["Elastic"]
description = """
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. Additionally, automated Linux fleets tend to see activity from rarely used usernames only when
personnel log in to make authorized or unauthorized changes, or threat actors have acquired credentials and log in for
malicious purposes. Unusual usernames can also indicate pivoting, where compromised credentials are used to try and move
laterally from one host to another.
"""
false_positives = [
    """
    Uncommon user activity can be due to an engineer logging onto a server instance in order to perform manual
    troubleshooting or reconfiguration.
    """,
]
from = "now-45m"
interval = "15m"
license = "Elastic License v2"
machine_learning_job_id = ["v3_linux_anomalous_user_name"]
name = "Unusual Linux Username"
note = """## Triage and analysis

### Investigating an Unusual Linux User
Detection alerts from this rule indicate activity for a Linux 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 troubleshooting or debugging activity by a developer or site reliability engineer?
- Examine the history of user activity. If this user only manifested recently, it might be a service account for a new software package. If it has a consistent cadence (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."""
references = ["https://www.elastic.co/guide/en/security/current/prebuilt-ml-jobs.html"]
risk_score = 21
rule_id = "b347b919-665f-4aac-b9e8-68369bf2340c"
severity = "low"
tags = ["Elastic", "Host", "Linux", "Threat Detection", "ML", "Machine Learning", "Initial Access"]
type = "machine_learning"

[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1078"
name = "Valid Accounts"
reference = "https://attack.mitre.org/techniques/T1078/"


[rule.threat.tactic]
id = "TA0001"
name = "Initial Access"
reference = "https://attack.mitre.org/tactics/TA0001/"