Is Your PC Part of a Botnet? Signs of Compromise

What Is a Botnet?

Imagine your computer silently sending spam emails, launching attacks on websites, or mining cryptocurrency—all without your knowledge or permission. This is what happens when your PC becomes part of a botnet, a network of infected computers controlled remotely by cybercriminals.

Botnet malware is designed to operate invisibly, like a sleeper agent hiding on your system. Your computer appears normal, but in the background, it's being used for malicious purposes. The concerning part? Many people never realize their PC is infected because modern botnets are engineered to avoid detection and maintain a low profile.

Understanding the warning signs can help you detect and remove botnet infections before they cause serious damage to your system, privacy, or internet connection.

Warning Signs Your PC Might Be in a Botnet

Performance Issues

• Slow performance when idle - Your PC runs slowly even when you're not using demanding programs
• Fan runs constantly - The cooling fan kicks into overdrive when your computer should be idle, indicating a program is using resources without your knowledge
• High CPU or memory usage - Task Manager shows high resource usage without obvious cause
• Programs open or close unexpectedly - Application windows appear or disappear on their own
• Long shutdown times - Your computer takes unusually long to shut down or won't shut down properly

Network Activity

• Internet slows to a crawl - If a botnet is using your computer to send massive amounts of spam or participate in attacks, your internet connection will be noticeably slower
• Unusual network activity - Spikes in data usage or connections to unfamiliar IP addresses when you're not actively browsing
• High bandwidth usage when idle - Your network activity monitor shows traffic even when you're not using the internet

System Behavior

• Cannot download Windows updates - Botnet malware often prevents operating system updates to maintain its foothold
• Antivirus disabled or won't update - Inability to update antivirus software or visit security vendors' websites is a strong indicator of malware
• Unexpected shutdowns or restarts - The computer restarts or shuts down without warning
• New programs or browser toolbars - Software you didn't install appears on your system

Communication Issues

• Friends receive spam from you - Family and contacts report receiving email messages from you that you didn't send
• Your accounts are locked - Email or social media accounts get locked due to suspicious activity
• Pop-ups when browser is closed - Advertisements appear even when you're not using a web browser

How to Check if Your PC Is Compromised

Step 1: Check Running Processes

1. Press Ctrl+Shift+Esc to open Task Manager
2. Click the "Processes" tab and sort by CPU or Memory usage
3. Look for unfamiliar processes using significant resources
4. Research suspicious process names online—legitimate Windows processes should have recognizable names and publishers
5. Be suspicious of:
   • Random letter combinations
   • Processes running from temporary folders
   • Multiple instances of the same program when only one should run

Step 2: Monitor Network Activity

1. In Task Manager, go to the "Performance" tab
2. Click "Ethernet" or "Wi-Fi" to see network activity
3. Watch for network activity when you're not actively using the internet
4. For detailed analysis, download Wireshark or GlassWire (free tools) to monitor exactly what connections your PC is making
5. Look for repeated connections to the same unfamiliar IP addresses

Step 3: Check Startup Programs

1. In Task Manager, go to the "Startup" tab
2. Review all programs set to start with Windows
3. Disable anything unfamiliar or suspicious by right-clicking and selecting "Disable"
4. Research program names you don't recognize before disabling critical system programs

Step 4: Review Installed Programs

1. Go to Settings > Apps > Installed apps
2. Sort by install date to see recently added programs
3. Uninstall any programs you don't recognize, especially those installed recently when unusual behavior started

Step 5: Check DNS Settings

Botnets sometimes modify DNS settings to redirect your traffic:

1. Go to Settings > Network & Internet
2. Click on your connection (Ethernet or Wi-Fi)
3. Scroll down and click "Hardware properties"
4. Check DNS server addresses—they should either be from your ISP or known public DNS like Google (8.8.8.8) or Cloudflare (1.1.1.1)
5. Unfamiliar DNS addresses might indicate DNS hijacking

How to Remove Botnet Malware

Step 1: Disconnect from the Internet

Immediately disconnect from the internet to prevent the botnet from communicating with its command and control server and potentially causing more damage.

Step 2: Boot into Safe Mode

1. Go to Settings > System > Recovery > Advanced startup
2. Click "Restart now"
3. Choose Troubleshoot > Advanced options > Startup Settings > Restart
4. Press 4 or F4 to boot into Safe Mode with Networking

Step 3: Run Comprehensive Malware Scans

1. Run Windows Defender Offline:
   • This scans before Windows fully loads, catching malware that hides from normal scans
   • Go to Windows Security > Virus & threat protection > Scan options > Microsoft Defender Offline scan
2. Install and run Malwarebytes:
   • Download from malwarebytes.com (use a clean device if necessary)
   • Run a full system scan
   • Malwarebytes excels at detecting botnet and rootkit malware
3. Use additional scanners:
   • Try Kaspersky TDSSKiller for rootkit detection
   • Run HitmanPro for secondary scanning

Step 4: Clean Browser and System

1. Remove suspicious browser extensions
2. Clear browser cache and cookies
3. Reset browser settings to defaults
4. Change all important passwords (email, banking, social media) from a clean device

Step 5: Update Everything

1. Update Windows to the latest version
2. Update all installed software, especially browsers and security software
3. Update drivers, particularly network drivers

Step 6: Verify Removal

1. Restart in normal mode and monitor system behavior
2. Run scans again to confirm malware is gone
3. Monitor Task Manager for suspicious activity over several days
4. Check that DNS settings remain correct

Prevention: Protecting Against Botnets

• Use antivirus with real-time protection - Keep Windows Defender or a reputable third-party antivirus active and updated
• Enable firewall - Windows Firewall should always be on to block unauthorized network connections
• Keep software updated - Botnets exploit vulnerabilities in outdated software
• Don't click suspicious links or attachments - Email attachments and links in messages are common infection vectors
• Be cautious downloading free software - Download only from official sources, not third-party download sites
• Use standard user accounts - Don't use administrator accounts for daily tasks
• Monitor network activity - Occasionally check Task Manager or use monitoring tools to watch for unusual activity