Your Eyes on Suspicious RDP Logins

Estimated read time 4 min read

Hello, fellow threat hunters! If you’re here, you’re obviously on the prowl for malicious activities in your network. Today, we’re looking at an old favorite for cybercriminals – Remote Desktop Protocol (RDP) exploits. These sneaky maneuvers have been around for years, but they’re just as dangerous today as they were back in the day. Here’s a straightforward guide on how to catch suspicious RDP logins red-handed.

Familiarize Yourself with RDP Traffic

The first step? Know your RDP. Get familiar with how typical Remote Desktop Protocol traffic behaves in your network. It’ll be your baseline. Remember, RDP usually uses TCP port 3389 or UDP port 3389.

Enable Auditing for RDP Login Attempts

Never underestimate your Event Viewer. To sniff out RDP login attempts, enable logging. This can be found under “Local Policies” > “Audit Policy” > “Audit logon events“. With this, you’ll get both successful and failed login attempts. Failed attempts might indicate a brute-force attack.

Monitor User Behavior

Now, let’s get a little deeper. User behavior analytics (UBA) can be your best pal here. If a user who typically works 9-to-5 starts logging in through RDP at 3 AM, that’s suspicious, right? UBA tools can help you track these anomalies. Don’t neglect this.

Check Multiple Failed Logins

As I said earlier, multiple failed logins may point to a brute-force attack. If an account has multiple failed logins within a short span, raise that red flag. Use Event Viewer and filter Event ID 4625 to identify these cases.

Geo-locate IP Addresses

Next up, we have geolocation. If RDP connections are coming from places where you have no business operations or remote employees, it’s time to sit up and take notice. IP geolocation tools are your go-to in such scenarios.

Analyze Session Durations

It’s not just about login times. A long RDP session could also signal malicious activity. Maybe someone’s lingering in the network, trying to install malware, or perform lateral movement. Keep a sharp eye on these prolonged sessions.

Leverage AI-Based Tools

Use AI to your advantage. Machine learning algorithms can sift through mountains of log data quickly and identify anomalies that may indicate an attack. Plenty of security information and event management (SIEM) tools now incorporate AI. Use them!

How Prolonged Patterns Reveal Threats

Okay, folks, let’s dive a bit deeper. Cyber threats don’t always hit with a bang – they’re often more like a slow drip. This is what we call the ‘long con’ of cybercriminal behavior.

Suspicious signs related to Remote Desktop Protocol (RDP):
Suspicious signs related to Remote Desktop Protocol (RDP):

Imagine this. It’s the first of February. All’s quiet on your network. But unbeknownst to you, a cybercriminal is launching their first recon mission. Their goal? To understand your network. To see your weak spots.

Fast forward to the 5th of February. Our cybercriminal is now at the next stage – launching slow, steady brute force attacks. They’re patient. They’re persistent. And if you’re not vigilant, they’ll break through.

Suddenly, it’s the 13th of February. The slow drip has become a flood. Our cybercriminal has a successful login. They’re in.

At first glance, these events may seem insignificant – easily overlooked in the daily rhythm of log events. However, if you dig a bit deeper, you’ll see a pattern emerge. This gradual buildup of suspicious activity is a hallmark of targeted attacks.

And why is this pattern targeting specific users or user ranges? Perhaps there’s been a data leak that includes their information. Maybe these users have privileges that make them appealing to cybercriminals. There could be any number of reasons. The key point here is that these targeted attacks don’t happen in a vacuum. They are planned, executed, and often successful unless detected and disrupted early.

So, what does this mean for you, the diligent threat hunter? It means you must stay alert. Stay vigilant. Each event in your logs isn’t just a standalone incident. Each one is a piece of a larger puzzle that, when put together, could signal an ongoing or impending attack.

When you see that successful login, it’s often too late. That’s when the real chaos begins. The key is to spot the clues before that moment, to disrupt the slow rhythm of the attack before it reaches its crescendo.

Keep your eyes wide open, threat hunters. Don’t let the slow drip of intrusion become a flood.

Reza Rafati

Reza Rafati, based in the Netherlands, is the founder of An industry professional providing insightful commentary on infosec, cybercrime, cyberwar, and threat intelligence, Reza dedicates his work to bolster digital defenses and promote cyber awareness.

You May Also Like

More From Author