| ID | Name |
|---|---|
| T1563.001 | SSH Hijacking |
| T1563.002 | RDP Hijacking |
Adversaries may hijack a legitimate user's SSH session to move laterally within an environment. Secure Shell (SSH) is a standard means of remote access on Linux and macOS systems. It allows a user to connect to another system via an encrypted tunnel, commonly authenticating through a password, certificate or the use of an asymmetric encryption key pair.
In order to move laterally from a compromised host, adversaries may take advantage of trust relationships established with other systems via public key authentication in active SSH sessions by hijacking an existing connection to another system. This may occur through compromising the SSH agent itself or by having access to the agent's socket. If an adversary is able to obtain root access, then hijacking SSH sessions is likely trivial.[1][2][3][4]
SSH Hijacking differs from use of SSH because it hijacks an existing SSH session rather than creating a new session using Valid Accounts.
| ID | Name | Description |
|---|---|---|
| S1220 | MEDUSA |
MEDUSA can be configured to capture SSH credentials via SSH hijacking.[5] |
| ID | Mitigation | Description |
|---|---|---|
| M1042 | Disable or Remove Feature or Program |
Ensure that agent forwarding is disabled on systems that do not explicitly require this feature to prevent misuse. [6] |
| M1027 | Password Policies |
Ensure SSH key pairs have strong passwords and refrain from using key-store technologies such as ssh-agent unless they are properly protected. |
| M1026 | Privileged Account Management |
Do not allow remote access via SSH as root or other privileged accounts. |
| M1022 | Restrict File and Directory Permissions |
Ensure proper file permissions are set and harden system to prevent root privilege escalation opportunities. |
| ID | Name | Analytic ID | Analytic Description |
|---|---|---|---|
| DET0256 | Detection Strategy for SSH Session Hijacking | AN0710 |
Suspicious reuse of SSH agent sockets across multiple users or processes, anomalous access to ~/.ssh/ or /tmp/ssh-* sockets, and abnormal patterns of lateral movement via SSH without new authentication events. Defender view: detect when one process accesses another user's SSH agent or when an existing SSH connection is used to pivot unexpectedly. |
| AN0711 |
Unusual access to SSH agent sockets in /tmp/ or /private/tmp, process access to another user’s $SSH_AUTH_SOCK, and lateral SSH activity without corresponding login events. Defender view: correlation of socket access with anomalous network flows to internal systems. |