What Is Remote Desktop Protocol? And How to Secure It

Remote access is essential to how organizations operate today. From businesses and schools to hospitals and government agencies, the ability to connect to systems from anywhere keeps operations running smoothly. Remote Desktop Protocol (RDP) plays a key role in making that possible.

Remote Desktop Protocol (RDP) is a Microsoft technology that lets people use one computer to access another from a different location over the internet. RDP is commonly used for remote work, IT support, and managing systems off-site.

In other words, it gives users full access to the remote machine’s desktop, including its files, applications, and system resources, just as if they were sitting in front of it. RDP is commonly used for remote work, IT support, and server management.

But when RDP connections aren’t properly secured, attackers can exploit these connections to move deeper into an organization’s network. It’s a common entry point in many post-compromise attacks Abnormal tracks. As a Microsoft partner, Abnormal helps detect and stop these threats before they escalate.

RDP works by creating an encrypted connection between two devices, typically a user’s local machine and a remote computer, over the internet. This allows full control of the remote system, almost as if the user were physically in front of it.

Here’s a simplified breakdown of how the process works:

• Connection Initiation: The RDP client starts a connection to the target computer using TCP port 3389, the default port for RDP traffic. For better performance in graphics-heavy use cases, RDP can also use UDP.

• Authentication and Security: Before anything is displayed, Network Level Authentication (NLA) verifies the user’s credentials. This prevents unauthorized users from even reaching the login screen.

• Session Setup: Once authenticated, the server creates a session based on the client’s settings—screen resolution, color depth, and device redirection preferences.

• Input and Response: User actions (like mouse movements and keystrokes) are sent as small encrypted packets. The server processes them and sends back only the parts of the screen that have changed.

• Performance Optimization: Compression, caching, and efficient rendering keep bandwidth use low and response times fast, even on slower networks.

• Data Protection: TLS encryption secures the entire session, assuming both systems are up to date and properly configured.

From the user’s perspective, the remote desktop behaves like a regular window on their local screen. Behind the scenes, RDP handles everything from device redirection to licensing checks, all in real time.

RDP's convenience can sometimes come at the cost of security. While it enables remote access at scale, its design and widespread misconfiguration make it a high-value target for threat actors. This section outlines the most critical vulnerabilities inherent in RDP deployments.

Improperly configured or internet-exposed RDP servers consistently rank among the preferred entry points for ransomware operators. Even when administrators move services away from the default TCP port 3389, attackers use automated scanning tools to sweep large IP ranges, probing for common alternatives like 1098. Once identified, these endpoints become prime targets for intrusion attempts.

Brute force attacks on RDP connections are still highly effective, especially when accounts use weak or reused passwords. Without enforced complexity rules or multi-factor authentication, attackers can automate login attempts until they find valid credentials. The risk compounds when RDP and VPN credentials are shared across systems or compromised through phishing campaigns.

Older RDP implementations rely on weak encryption and may not enforce critical protections like Network Level Authentication (NLA). Without modern TLS configurations, attackers can intercept sessions or trigger pre-authentication flaws. TheBlueKeep vulnerability (CVE-2019-0708) is a prime example, enabling unauthenticated remote code execution and rapid wormable spread across unpatched systems.

Despite frequent updates from Microsoft, many RDP-enabled systems remain unpatched for extended periods. This creates a window of opportunity for attackers to exploit known issues, even when fixes are available. Security researchers continue to discover exposed RDP endpoints running outdated services with publicly known vulnerabilities.

Many organizations fail to enforce least-privilege access on RDP accounts. Users often connect with administrative privileges, and access controls are rarely segmented by role or job function. This overprovisioning, combined with a lack of network segmentation, gives attackers full lateral movement once a session is compromised, turning a single RDP foothold into an enterprise-wide threat.

A properly-secured RDP environment reduces risk and closes off one of the most consistently abused entry points in enterprise networks. These best practices focus on actionable changes your security team can implement today to harden RDP access without overhauling your infrastructure.

Strong password policies form the foundation of RDP security. Brute-force attacks become exponentially harder when credentials are unique, complex, and not reused across systems. Encourage the use of password managers to eliminate human guessability.

Multifactor Authentication (MFA) is a must. Even if credentials are phished, attackers are blocked without a second authentication factor, significantly reducing the risk of unauthorized access.

Network Level Authentication (NLA) adds another layer by requiring credentials before a session is established. Pair this with access management tools to apply least privilege across accounts—elevated access should only be granted when explicitly needed.

Change the default RDP port (3389) to a non-standard option to deter basic automated scans. While not a primary defense, this simple tweak filters out many opportunistic attacks.

Firewall rules should only permit RDP access from trusted IP ranges or authorized VPN gateways. Never expose RDP directly to the public internet.

Implement jump servers or RDP gateways to centralize authentication and logging. These systems act as secure chokepoints, reducing the attack surface across your broader environment.

Use account lockout policies to stop brute-force attempts after repeated failed logins. Tune thresholds to prevent disruption while still protecting accounts from enumeration.

Log all RDP sessions and analyze them for abnormal behaviors. Watch for strange login hours, unusual locations, or excessive resource usage—common signs of compromise.

Monitor for compromise attempts by correlating RDP activity with email alerts, endpoint telemetry, and authentication anomalies.

Deploy self-signed certificates internally to control who can connect via RDP. Certificate-based access adds cryptographic validation, limiting exposure even when usernames and passwords are leaked.

This is particularly effective for managing internal traffic without investing in external certificate infrastructure.

Privileged Access Management (PAM) solutions help limit the blast radius of any single compromised account. Store RDP credentials in encrypted vaults, enforce access through approval workflows, and log every privileged session.

Avoid giving direct admin rights to users. Instead, use PAM to issue time-bound credentials with specific task scopes.

Always apply security updates to RDP components, Windows Server, VPNs, firewalls, and MFA tools. Exploits targeting unpatched systems often surface within days of disclosure.

Minimize public exposure by restricting RDP access to private networks and known IPs. This single step prevents most commodity attacks from even reaching your endpoints.

Do not allow users to access RDP without proper security awareness training. Topics should include password hygiene, VPN usage, MFA protection, and the importance of not sharing remote access credentials.

Make sure employees can identify phishing attempts targeting RDP credentials and know how to report suspected compromises.

Organizations face increasingly advanced credential phishing and social engineering campaigns targeting remote access systems like RDP. Abnormal’s AI-powered email protection detects and stops these threats in real time, often before credentials are ever compromised. For enterprises seeking stronger remote access security, it’s worth considering how Abnormal fits into your defense strategy.

Audit your systems and disable RDP on endpoints that don’t require remote access, such as single-purpose servers, kiosks, or tightly scoped production workloads.

This reduces your total attack surface and makes it harder for threat actors to find accessible targets.

RDP will always be a target, but it doesn’t have to be a weakness. When configured with layered controls across authentication, network access, monitoring, and user education, RDP can offer secure, reliable remote access without exposing your environment to unnecessary risk.

For enterprise security teams, the path forward isn’t about finding a silver bullet—it’s about tightening each layer, removing legacy exposures, and aligning remote access with broader zero-trust initiatives. The threats targeting RDP aren’t going away, but with the right strategy, neither is your control.

Abnormal helps prevent credential phishing attacks that often precede RDP compromise, detecting social engineering attempts that other systems miss. To see how Abnormal fits into your layered defense strategy, request a personalized demo today.