Stop EXE File Brute-Force Attacks

TL;DR

Someone is trying to guess passwords to access your executable file. We’ll show you how to identify the attack, block the attacker, and strengthen your security.

1. Understand the Attack

A brute-force attack on an EXE file means someone is repeatedly trying different username/password combinations to gain unauthorized access. This usually happens when:

• Your application doesn’t have strong password policies (e.g., short passwords, no complexity requirements).
• You haven’t implemented account lockout after multiple failed attempts.
• The EXE file has a vulnerability allowing password guessing.

2. Identify the Attack

Look for these signs:

• Event Logs: Check your Windows Event Viewer (Security logs) for repeated failed login attempts from the same IP address or user account.
• Application Logs: Your application may log failed logins. Examine those logs for patterns.
• Resource Usage: A sudden spike in CPU usage could indicate a brute-force attempt, though this isn’t always conclusive.

Example Event Log entry (look for Event ID 4625 – Failed Login):

Event ID: 4625

Source: Microsoft-Windows-Security-Auditing

Account Name: [Attacker Account]

Workstation Name: [Attacker IP Address]

3. Block the Attacker

There are several ways to block the attacker:

• Firewall: Block the attacker’s IP address in your Windows Firewall or network firewall.
• Open Windows Defender Firewall with Advanced Security.
• Create a new Inbound Rule.
• Select Custom and specify the IP address to block.
• Router: Block the attacker’s IP address in your router’s settings (if possible).
• Application Level Blocking: If your application allows it, temporarily disable access from suspicious IPs within its configuration.

4. Strengthen Your Security

These steps will make future attacks much harder:

• Strong Passwords: Enforce strong password policies (minimum length, complexity requirements – uppercase, lowercase, numbers, symbols).
• Account Lockout: Implement account lockout after a certain number of failed login attempts. For example, lock the account for 30 minutes after 5 incorrect passwords. This is usually configured within your application or Active Directory (if used).
• Multi-Factor Authentication (MFA): Add MFA to your application if possible. This requires a second form of verification (e.g., code sent to phone) in addition to the password.
• Update Your Application: Ensure you’re running the latest version of your application, as updates often include security patches that address vulnerabilities.
• Code Review: If you developed the EXE file yourself, have a security expert review the code for potential weaknesses.

5. Monitor Your System

Continue to monitor your event logs and application logs for suspicious activity even after blocking the initial attacker. Regularly review your security settings.