What Is a Botnet? How Botnets Work, Dangers, and Protection Tips

Botnet is a network of infected computers, servers, smartphones, routers, and other devices that can be remotely controlled by a cybercriminal without the owners' knowledge. Each device in such a network is called a bot or "zombie": it continues to perform regular tasks, but can simultaneously receive commands from outside.

The main danger of a botnet lies in its scale. A single infected computer can cause limited harm, but tens of thousands of devices acting together become a powerful tool for DDoS attacks, mass spam campaigns, malware distribution, and other illegal activities.

Botnet operators don't need to manually connect to each device. The control is designed so a single command can automatically propagate across the entire network. This is why botnets can unite massive numbers of devices and act as a single distributed system.

Botnet Explained in Simple Terms

The word botnet comes from "bot" and "network." In essence, it's a group of devices infected with malware that can now execute commands from a single operator. The owner of a computer, smartphone, or router is often completely unaware their device has become part of someone else's infrastructure.

Each infected device in a botnet is called a bot or "zombie." It doesn't always stop working normally: users can browse websites, watch videos, and launch programs as usual. The malicious component works in the background, maintains contact with the control system, and waits for new instructions.

Botnets can include not just personal computers. Cybercriminals infect servers, smartphones, home routers, IP cameras, network storage, and other Internet of Things (IoT) devices. Devices that are always connected to the internet and rarely updated are especially attractive targets.

This means the power of an individual device isn't crucial for a botnet. Even thousands of relatively weak routers or cameras together can generate an immense volume of network traffic. The larger the network, the more resources the operator has for attacks.

How a Device Becomes Part of a Botnet

How Infection Occurs

To add a device to a botnet, an attacker first needs to install a malicious component. This can happen through infected attachments, fake apps, malicious websites, or vulnerabilities in the operating system or applications. Sometimes infection happens almost without user involvement, especially if the device is accessible from the internet and contains a known vulnerability.

Routers, IP cameras, and other IoT devices pose a unique problem. They can run for years with outdated firmware, open network services, or default manufacturer passwords. Automated programs scan the internet for such devices, then attempt to access them and install botnet code.

The infection process is similar to the spread of other malware. To learn more about how malicious software infiltrates and persists on a system, read our guide: Ransomware explained: how modern attacks work and how to defend against them.

What Happens After Infection

After launch, the malware tries to establish persistence and ensure it runs after a reboot. Next, it connects to the botnet infrastructure and reports a new available device.

The bot usually enters a standby mode, periodically checking in with a command server for new instructions and sending technical information about the system. If no commands are issued, its activity is minimal, so the user may not notice any changes.

When the botnet operator needs resources, the infected device receives a command and acts alongside other network members. This could involve sending network requests, downloading additional malware, distributing messages, or other tasks.

This stealth is what makes botnets durable. Owners continue using their devices, unaware that part of their computing power and internet connection is controlled by someone else.

How Botnets Control Thousands or Millions of Devices Simultaneously

Centralized Control via C2

A classic botnet is built around Command and Control (C2) infrastructure-a server or group of servers through which the operator sends commands to infected devices. Each bot regularly contacts the C2 server to check for tasks and report its status.

This approach allows the operator to manage massive networks without directly connecting to every device. One command is sent to the control server, and thousands or even millions of bots receive it, carrying out the task almost simultaneously. This enables botnets to generate sudden, immense traffic or computing loads.

Devices can be spread across countries and run on different hardware. For the management system, this doesn't matter: each bot acts according to its programming and executes commands automatically.

However, centralized schemes have a clear downside. If security professionals detect and take down the control servers, a significant portion of the botnet may lose its ability to receive new commands. That's why more advanced networks use backup servers, change infrastructure addresses, or employ alternative communication methods.

P2P Botnets

In a P2P (peer-to-peer) botnet, there may be no central control point. Infected devices connect to each other, forming a distributed network similar to regular peer-to-peer systems. A command received by one bot can be passed along to others.

This design makes botnets more resilient. Even if some infected devices or nodes go offline, the rest can still exchange information. Disrupting such a network requires more than just locating one control server.

This distributed architecture explains how a single operator can control vast numbers of infected devices at once. They manage the entire system through automated command propagation-not by manually directing each computer.

What Botnets Are Used For and Why They're Dangerous

DDoS Attacks

One of the most well-known uses for botnets is launching DDoS attacks. Here, a large number of infected devices simultaneously send requests to a website, server, or online service. If the traffic volume becomes too great, the infrastructure is overwhelmed and regular users lose access.

The main advantage of a botnet in these attacks is its distributed nature. Requests come from thousands of different IP addresses worldwide, making traffic filtering difficult and generating loads that can't be replicated by a single device.

Even weak routers, cameras, or other IoT devices become dangerous in large numbers. While a single bot may generate only small amounts of traffic, tens of thousands can strain networks and servers severely.

Botnets are just one tool in modern cyberattacks. For a deeper look at other threats and protection strategies, check out our article: Cybersecurity in 2026: new threats, trends, and top protection technologies.

Other Botnet Purposes

Botnets aren't just for DDoS. Infected devices often participate in mass spam and phishing campaigns. The more bots in a network, the more messages can be sent quickly-and the harder it is to block the source.

Botnets can also distribute additional malware. After infection, the device becomes an entry point for the operator to upload more programs, change system configurations, or use it for further attacks.

Another use is leveraging the victim's internet connection as a proxy. Here, malicious traffic passes through the infected device, and external services see the IP address of a regular user, not the real botnet operator.

Some botnets can steal credentials, intercept information, exploit device computing resources, or automate actions on websites. This means the danger isn't limited to large-scale attacks on others: an infected device itself becomes part of a criminal infrastructure and can be used without the owner's knowledge.

How to Tell If Your Device Is in a Botnet and How to Protect Yourself

Possible Signs of Infection

Detecting a botnet infection at home isn't always easy. Malware tries to remain hidden, so the user may not see obvious windows, warnings, or new programs. Sometimes the only clues are indirect.

• Unusually high CPU or network usage, especially when the device is idle
• Performance slowdowns, overheating, rapid battery drain, or unknown running processes
• On routers and network devices, constant data exchange even without regular activity

One symptom alone doesn't prove infection-updates, cloud syncing, or normal apps can also cause high loads. Suspicion increases if strange activity persists, appears suddenly, or is accompanied by unknown network connections or settings changes.

How to Reduce Infection Risk

One of the most effective protection methods is promptly installing updates for operating systems, software, and device firmware. Many botnets spread automatically by finding devices online with known vulnerabilities.

Pay special attention to routers and IoT devices. Default admin passwords should be changed immediately after setup. If remote management over the internet isn't needed, disable it. For cameras, network storage, and similar devices, check for new firmware updates regularly.

On computers, use up-to-date security tools and avoid opening unknown attachments or software from untrusted sources. For a detailed look at basic digital safety, see our guide: Cybersecurity for beginners: essential tips for 2025.

If you seriously suspect infection, scan your computer with security software and remove any detected threats. For routers and some IoT devices, updating firmware or resetting to factory settings and setting a new password may be necessary.

After cleanup, it's crucial to address the root cause. Leaving outdated firmware, open remote access, or a weak password could result in reinfection soon after recovery.

Conclusion

A botnet is not just a single infected computer, but an entire network of devices executing the commands of a remote operator. Malware first infects a device-computer, server, router, or IoT device-then connects it to a control infrastructure, allowing the bot to receive commands alongside thousands of others.

The strength of a botnet lies in its scale. Even relatively weak devices, combined into a unified system, can generate enormous traffic, send messages, distribute malware, and participate in other attacks. Meanwhile, owners may remain unaware for a long time that their devices are being misused.

To reduce the risk of becoming part of a botnet, it's essential to keep systems and firmware updated, change default passwords, disable unnecessary remote access, and monitor unusual network activity. This is especially important for routers, cameras, and other always-online devices that often go unpatched for years.