How to Detect, and Then Stop, Botnet Malware on Your Network

Coffee number three. Let’s talk about botnets.

Quick Take

• If you’re a cybercriminal, you love botnets because they allow you to launch attacks at scale.
• Once malware gets into a device, it can zap it into forming part of a botnet without users the wiser.
• You can block botnet traffic—but only if you take steps to do so.
• PJ Networks sets Fortinet security solutions that can block botnets at the user-end before they take root.

What is a Botnet?

A botnet is a network of hacked devices—laptops, servers, or even connected gadgets—that have been infected with malware and are currently in a hacker’s control. Consider it a zombie army where, instead of munching your brain, it’s performing DDoS attacks, exfiltrating data, or deploying more malware.

It’s not only that guy clicking sketchy links, either. Businesses get targeted. Botnets have taken down banks, healthcare companies, even critical infrastructure. You don’t need a gaping security hole — often all it takes is one unpatched router or a misconfigured firewall.

I witnessed this firsthand with the Slammer worm in 2003. It burst around the world in a matter of minutes, attacking SQL vulnerabilities and knocking out network after network. That was chaos. Today’s botnets? Smarter. Harder to detect. But still stoppable.

How Does Malware Convert Devices into Bots?

Here’s the thing — infection is extremely easy. Malware is carried out by attackers via:

• Phishing Emails (Yes, people still open shady attachments)
• Targeting unpatched software
• Compromised remote desktop access (RDP brute-force is still rampant)
• Malicious advertisements (malvertising)
• Infected USB drives (Flashbacks to Stuxnet).

Once the malware is in, it:

1. Calls home to a command-and-control (C2) server—Sort of like a soldier reporting home for orders.
2. Begins listening for commands—May be waiting to execute DDoS, send spam, mine crypto.
3. Spreads Horizontally–Nuking other devices on the network

And here’s the really evil part: Most devices infected with this malware don’t display blatant symptoms. Your laptop’s not going to start puffing smoke. But perhaps it’s not as speedy as it could be? Perhaps there’s unusual outgoing traffic at strange hours? It’s why network monitoring is important.

How to Block Botnet Traffic

You cannot count on your firewall already having this potential taken care of. Most of the botnet infections “blend in” with normal traffic. So what do you do?

1. (Load & Traffic Monitoring of Outbound Traffic Especially for DNS & Command Traffic)
   • Identify abnormal spikes in outbound connections
   • Look for communications with odd IP addresses.
   • Block known C2 domains and IPs—this is where actual threat intel is useful.
2. Limit Unused Services & Open Ports
   • Disable all unused Telnet (23), RDP (3389), FTP (21)
   • Leverage least-privilege access — why provide greater access than necessary?
3. DNS Filtering & Web Security Deployment
   • DNS tunneling is used to hide traffic in many botnets. Banning them at the DNS level starves connections.
   • Web filtering can also prevent access to malicious domains prior to infection.
4. Use Network Segmentation
   • Suppose one machine gets infected — does that mean your whole network is compromised?
   • Isolate critical systems to limit the spread of infection.
5. Approach #3: Leverage Threat Intelligence & Automated Detection
   • Good IPS/IDS (intrusion prevention/intrusion detection system) gets these sorts of botnet-like activity.
   • AI-powered security tools? Meh. Too many false positives. I prefer behavior-oriented detection with real analytics.

Bottom line? Signature-based antivirus is not enough: you need active monitoring and layered defenses.

Fortinet Security Solutions — PJ Networks

At PJ Networks, we are a company who catches and destroys these botnets before they reach havoc. We’ve been doing this decades, and Fortinet is one of the best security stacks for being ahead of the threat.

What We Deploy:

• ✅ FortiGate NGFWs – Threat detection with context and deep analytics
• ✅ FortiAnalyzer – A record of every possible threat, ensuring nothing goes unnoticed.
• ✅ FortiNAC – Implements zero-trust principles to prevent lateral movement
• ✅ FortiSandbox – Serves zero-day malware prevention before any executables run

We recently assisted three banks in enhancing their zero-trust architecture — and you would not believe the volume of botnet attempts they were experiencing on a daily basis. They even still had some of their old setups communicating live with command-and-control servers, completely under the radar before we intervened.” That’s the risk of botnets — they don’t draw attention. They sit there, just funneling out data in silence.

So, we locked down outbound traffic, added DNS-layer security, and hardened our endpoint defenses with Fortinet’s threat intelligence. In the coming days, we took down several botnet infections when they were just ramping up.

Conclusion

Botnets aren’t just a problem—they’re a major business threat. Whether it’s data theft, launching attacks, or resource depletion, they’re a constant threat that needs to be actively defended against.

If you don’t know if your network has undetected botnet traffic, you need to monitor—the yesterday.

• Look at outbound communication logs.
• Deploy DNS-layer security.
• Block common C2 traffic.
• Segment critical assets.

We don’t sell security at PJ Networks, we harden networks. Free sleep can be yours; if botnets are sending you to be tormented, be it right in your network performance (for the web crawlers flush out there intact) Fortinet’s security stack — when it’s properly applied — will give you back the presence and controls you want.

Looking for an actual botnet defense strategy? Call us. Let’s discuss security — before your network becomes an employee of the bad guys.