Elastic Security Detection Rules

Login via Unusual System User

Last updated 7 months ago on 2025-01-15
Created 7 months ago on 2025-01-07

About

This rule identifies successful logins by system users that are uncommon to authenticate. These users have `nologin` set by default, and must be modified to allow SSH access. Adversaries may backdoor these users to gain unauthorized access to the system.
Tags
Domain: EndpointOS: LinuxUse Case: Threat DetectionTactic: PersistenceTactic: Defense EvasionData Source: SystemLanguage: eql
Severity
medium
Risk Score
47
MITRE ATT&CK™

Persistence (TA0003)(opens in a new tab or window)

↳ Account Manipulation (T1098)(opens in a new tab or window)

Defense Evasion (TA0005)(opens in a new tab or window)

↳ Hide Artifacts (T1564)(opens in a new tab or window)

License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Event Correlation Rule
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
filebeat-*logs-system.auth-*
Related Integrations

system(opens in a new tab or window)

Query
authentication where host.os.type == "linux" and event.action in ("ssh_login", "user_login") and
user.name in (
  "deamon", "bin", "sys", "games", "man", "lp", "mail", "news", "uucp", "proxy", "www-data", "backup",
  "list", "irc", "gnats", "nobody", "systemd-timesync", "systemd-network", "systemd-resolve", "messagebus",
  "avahi", "sshd", "dnsmasq"
) and event.outcome == "success"

Install detection rules in Elastic Security

Detect Login via Unusual System User in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).