Detect SSH in Elastic Security
Adversaries may use Valid Accounts to log into remote machines using Secure Shell (SSH). SSH allows authorized users to open remote shells on Linux, macOS, and ESXi systems. Adversaries leverage existing SSH keys or stolen passwords to pivot between systems. Notable actors using SSH for lateral movement include FIN7, Lazarus Group, Leviathan, Scattered Spider, BlackTech, and APT groups targeting cloud and ESXi environments. SSH lateral movement may also involve agent forwarding abuse, key theft, adding attacker-controlled public keys to authorized_keys files, or chaining through multiple hosts to obscure the original source.
MITRE ATT&CK
- Tactic
- Lateral Movement
- Technique
- T1021 Remote Services
- Sub-technique
- T1021.004 SSH
- Canonical reference
- https://attack.mitre.org/techniques/T1021/004/
Elastic Detection Query
sequence by host.name with maxspan=5m
[process where event.type == "start" and
process.name in ("ssh", "scp", "sftp", "ssh-agent", "ssh-add") and
(
process.args : "StrictHostKeyChecking=no" or
process.args : "-i" or
process.args : "ProxyJump" or
process.args : "ProxyCommand" or
process.args : "-D" or
process.args : "-L" or
process.args : "-R" or
process.args : "-N" or
process.command_line : "*authorized_keys*"
)
] by process.pid
| [any where true] by process.parent.pid
OR
sequence by host.name with maxspan=1h
[file where event.type in ("creation", "change") and
file.name == "authorized_keys" and
file.path : "*/.ssh/*"
]
[process where event.type == "start" and
process.name in ("ssh", "scp", "sftp")
]Detects suspicious SSH lateral movement patterns including tunnel creation, disabled host key checking, key-based authentication with explicit identity files, and unauthorized modifications to authorized_keys files on Linux/macOS endpoints. Uses ECS process and file event types with sequence correlation.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate system administrators using SSH tunnels for authorized remote access or jump hosts defined in corporate runbooks
- Automated deployment pipelines (Ansible, Terraform, Chef) that use SSH with custom keys and disable strict host checking for ephemeral infrastructure
- Backup or monitoring agents (e.g., rsync over SSH, Nagios NRPE) that modify authorized_keys as part of provisioning workflows
Other platforms for T1021.004
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1SSH Lateral Movement to Remote Host
Expected signal: Linux auditd EXECVE record for ssh binary with arguments. Syslog entry from sshd on target: 'Accepted password for testuser from <source_ip>'. Linux auditd USER_LOGIN event. Process creation for ssh child process.
- Test 2SSH SOCKS Proxy Tunnel Creation
Expected signal: Linux auditd EXECVE for ssh with -D 1080 -N -f flags. Process runs in background (due to -f flag). Network connection established on source port 1080 (SOCKS listener). Syslog entry on target for SSH connection.
- Test 3Add Attacker SSH Public Key to authorized_keys
Expected signal: Linux auditd OPEN event for ~/.ssh/authorized_keys with write flag. File modification timestamp change. Sysmon for Linux (if deployed): FileCreate/FileModify event for authorized_keys path.
- Test 4SSH Key-Based Lateral Movement with Stolen Key
Expected signal: Linux auditd EXECVE for ssh with -i /tmp/stolen_id_rsa. OPEN event for /tmp/stolen_id_rsa (private key access). Network connection to target port 22. Syslog on target: 'Accepted publickey for root'.
References (8)
- https://attack.mitre.org/techniques/T1021/004/
- https://man7.org/linux/man-pages/man1/ssh.1.html
- https://linux.die.net/man/8/sshd
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1021.004/T1021.004.md
- https://www.mandiant.com/resources/blog/unc3944-sms-phishing-sim-swapping
- https://www.crowdstrike.com/blog/carbon-spider-embraces-big-game-hunting/
- https://www.kaspersky.com/blog/lazarus-threatneedle/
- https://www.cisa.gov/uscert/ncas/alerts/aa22-108a
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