RDP Hijacking

What the technique is

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). 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. This can be done remotely or locally and with active or disconnected sessions. 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.

What MITRE says you would watch

• AN1620

  Detection of suspicious use of tscon.exe or equivalent methods to hijack legitimate RDP sessions. Defenders can observe anomalies such as session reassignments without corresponding authentication, processes spawned in the context of hijacked sessions, or unusual RDP network traffic flows that deviate from expected baselines.