RDP Brute Force Attack Detection

AuthenticationAttacks Windows Security RDP Brute Force

What This Means

Detect RDP brute force attacks using Windows Event logs. Protect Remote Desktop Protocol from automated password guessing with proper monitoring and hardening techniques.

Example Log

An account failed to log on.
Logon Type: 10
Account Name: Administrator
Source Network Address: 45.33.32.156
Failure Reason: Unknown user name or bad password.
Status: 0xC000006D

Indicators of Suspicious Activity

Event 4625 with Logon Type 10 (RemoteInteractive) from external IP addresses
Multiple RDP failures from a single IP targeting the Administrator account
Failures on port 3389 from geographic regions outside your user base
Sequential username attempts from the same source (admin, administrator, user)
Event 4625 Type 10 occurring outside business hours
Network connection logs showing sustained connections to port 3389

How to Investigate

Filter Event 4625 for Logon Type 10 and group by Source Network Address
Check if port 3389 is exposed to the internet (it should not be)
Correlate with firewall logs for connection attempts on RDP ports
Verify if NLA (Network Level Authentication) is enabled
Check for successful Type 10 logons (Event 4624) from the same source IPs
Review RDP connection broker logs if using Remote Desktop Services

Recommended Mitigations

Never expose RDP (port 3389) directly to the internet
Require VPN or RD Gateway for all remote desktop access
Enable Network Level Authentication (NLA) for RDP
Configure account lockout policies for RDP authentication
Deploy MFA for remote desktop connections
Use Windows Firewall or NSG rules to restrict RDP to known IP ranges

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Related Attack Patterns

Frequently Asked Questions

How do attackers find exposed RDP servers? ▼

Attackers use tools like Shodan, Masscan, and ZMap to scan the entire internet for open port 3389. Any server with RDP exposed to the internet will be discovered and attacked within hours.

What is the best protection against RDP brute force? ▼

Never expose RDP to the internet. Place it behind a VPN or RD Gateway. If internet exposure is unavoidable, enable NLA, enforce MFA, and use account lockout with fail2ban equivalent on Windows.

How do I check if RDP is exposed to the internet? ▼

Run an external port scan using nmap or check Shodan for your public IP. On the server, run netstat -an | findstr 3389 and verify the listening address is restricted, not 0.0.0.0.