Remote Desktop Protocol
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).  There are other implementations and third-party tools that provide graphical access Remote Services similar to RDS.
Adversaries may connect to a remote system over RDP/RDS to expand access if the service is enabled and allows access to accounts with known credentials. Adversaries will likely use Credential Access techniques to acquire credentials to use with RDP. Adversaries may also use RDP in conjunction with the Accessibility Features technique for Persistence. 
Adversaries may also 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 and prompted with a question. 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 RedSnarf. 
Disable the RDP service if it is unnecessary, remove unnecessary accounts and groups from Remote Desktop Users groups, and enable firewall rules to block RDP traffic between network security zones. Audit the Remote Desktop Users group membership regularly. Remove the local Administrators group from the list of groups allowed to log in through RDP. Limit remote user permissions if remote access is necessary. Use remote desktop gateways and multifactor authentication for remote logins.  Do not leave RDP accessible from the internet. Change GPOs to define shorter timeouts sessions and maximum amount of time any single session can be active. Change GPOs to specify the maximum amount of time that a disconnected session stays active on the RD session host server. 
Use of RDP may be legitimate, depending on the network environment and how it is used. Other factors, such as access patterns and activity that occurs after a remote login, may indicate suspicious or malicious behavior with RDP. Monitor for user accounts logged into systems they would not normally access or access patterns to multiple systems over a relatively short period of time.
Also, set up process monitoring for
tscon.exe usage and monitor service creation that uses
cmd.exe /k or
cmd.exe /c in its arguments to prevent RDP session hijacking.
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