Potential Linux SSH Brute Force Detectededit

Identifies multiple consecutive login failures targeting an user account from the same source address and within a short time interval. Adversaries will often brute force login attempts across multiple users with a common or known password, in an attempt to gain access to accounts.

Rule type: eql

Rule indices:

  • auditbeat-*
  • logs-system.auth-*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100


  • Elastic
  • Host
  • Linux
  • Threat Detection
  • Credential Access

Version: 1

Added (Elastic Stack release): 8.5.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guideedit

## Triage and analysis

### Investigating Potential SSH Brute Force Attack

The rule identifies consecutive SSH login failures targeting a user account from the same source IP address to the
same target host indicating brute force login attempts.

#### Possible investigation steps

- Investigate the login failure user name(s).
- Investigate the source IP address of the failed ssh login attempt(s).
- Investigate other alerts associated with the user/host during the past 48 hours.
- Identify the source and the target computer and their roles in the IT environment.

### False positive analysis

- Authentication misconfiguration or obsolete credentials.
- Service account password expired.
- Infrastructure or availability issue.

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved hosts to prevent further post-compromise behavior.
- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are
- Reset passwords for these accounts and other potentially compromised credentials.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
mean time to respond (MTTR).

Rule queryedit

sequence by host.id, source.ip, user.name with maxspan=10s
[authentication where event.action in ("ssh_login", "user_login") and
event.outcome == "failure" and source.ip != null and source.ip !=
"" and source.ip != "::" ] with runs=10

Threat mappingedit