The FBI & DHS issued a joint statement alerting businesses and consumers that cybercriminals are increasingly exploiting the Remote Desktop Protocol (RDP) administration tool.
The notice states that using RDP as an attack vector has been on the rise since 2016, with attackers using open RDP ports to hijack machines or intercepting RDP sessions and infecting the system being remotely accessed with different types of malware. There have also been several cases of systems with RDP software present that attackers have exploited by using brute-force techniques to gain access to usernames and passwords.
Attacks on RDP do not require user input and the intrusion itself is difficult to detect. By abusing RDP sessions, hackers can compromise identities, login credential, and demand ransom for other sensitive types of information.
Cybercriminals continue to develop new attack methods for exploiting vulnerable RDP sessions over the web and both business and consumers must take the necessary steps to reduce the likelihood of compromise. Hackers often target weak passwords, specific those with dictionary words or those that do not contain a combination of uppercase/lowercase/numbers/special characters, and those with outdated versions of RDP. Attackers also abuse unrestricted access to the default RDP port and unlimited login attempts to a user account.
CrySIS, CryptOn and SamSam ransomware have been known to spread through RDP attacks. CrySIS has been used mainly to target U.S. businesses that have computers with open RDP ports, using both brute force and dictionary attacks to gain unauthorized remote access. CrySIS then drops the ransomware onto the device and demands payment in Bitcoin for the decryption key.
CryptOn uses brute force attacks to gain access to RDP sessions, allowing the hacker to manually execute malicious programs on the compromised system. SamSam ransomware uses various exploits, including ones attacking RDP-enabled machines in order to perform brute force attacks.
Since RDP has the ability to remotely control a system entirely, organizations must closely regulate, monitor and control its usage. The FBI and DHS recommend taking the following steps to protect against RDP based attacks:
- Audit your network for systems using RDP; disable the service is not necessary and install available patches
- Verify that all cloud-based virtual instances with a public IP do not have open RDP ports, namely port 3389, unless there’s a specific business reason to do so. Place any system with an open RDP port behind a firewall and require users to use a VPN to access it through the firewall
- Enable strong passwords and account lockout policies to defend against brute force attacks
- Apply two-factor authentication, where possible
- Apply system and software updates regularly
- Enable logging and ensure logging mechanism capture RDP logins; keep logs for a minimum of 90 days to review and detect intrusion attempts
- Minimize network exposure for all control system devices; where possible, critical devices should not have RDP enabled.
- Regulate and limit external to internal RDP connections. When external access to internal resources is required, use secure methods, such as VPNs
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