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.

References

1. Duarte, H., Morrison, B. (2012). (Mis)trusting and (ab)using ssh. Retrieved January 8, 2018.
2. Adam Boileau. (2005, August 5). Trust Transience: Post Intrusion SSH Hijacking. Retrieved December 19, 2017.
3. Beuchler, B. (2012, September 28). SSH Agent Hijacking. Retrieved November 17, 2024.
4. Hodgson, M. (2019, May 8). Post-mortem and remediations for Apr 11 security incident. Retrieved November 17, 2024.

Adversaries may hijack a legitimate user’s remote desktop session to move laterally within an environment. Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS).^[1]

Adversaries may perform RDP session hijacking which involves stealing a legitimate user's remote session. Typically, a user is notified when someone else is trying to steal their session. With System permissions and using Terminal Services Console, c:\windows\system32\tscon.exe [session number to be stolen], an adversary can hijack a session without the need for credentials or prompts to the user.^[2] This can be done remotely or locally and with active or disconnected sessions.^[3] It can also lead to Remote System Discovery and Privilege Escalation by stealing a Domain Admin or higher privileged account session. All of this can be done by using native Windows commands, but it has also been added as a feature in red teaming tools.^[4]

References

1. Microsoft. (n.d.). Remote Desktop Services. Retrieved June 1, 2016.
2. Korznikov, A. (2017, March 17). Passwordless RDP Session Hijacking Feature All Windows versions. Retrieved December 11, 2017.
3. Beaumont, K. (2017, March 19). RDP hijacking — how to hijack RDS and RemoteApp sessions transparently to move through an organisation. Retrieved December 11, 2017.
4. NCC Group PLC. (2016, November 1). Kali Redsnarf. Retrieved December 11, 2017.