What Is a Botnet and How to Avoid Being Part of One
What Is a Botnet?
A botnet is a network of internet-connected devices that have been infected with malware and are secretly controlled by an attacker, who can command them collectively to perform malicious actions. The term combines "robot" and "network." Devices in a botnet — called "bots" or "zombies" — carry out the attacker's commands without their owners' knowledge. Botnets can comprise thousands or even millions of compromised devices, giving attackers enormous collective power.
Understanding botnets helps you avoid having your devices conscripted and recognize this significant threat.
How Devices Become Part of a Botnet
Devices are conscripted into botnets through malware infection:
Malware infection: A device becomes part of a botnet when infected with botnet malware, through the usual infection routes — phishing, malicious downloads, exploited vulnerabilities, and other malware.
Secret control: Once infected, the device secretly connects to the attacker's command-and-control infrastructure, awaiting commands, while continuing to function normally so the owner is unaware.
Collective command: The attacker commands the entire botnet collectively, directing all the compromised devices to act together.
Vulnerable devices: Poorly-secured devices — especially IoT devices with weak default credentials and unpatched vulnerabilities — are common botnet targets, easily conscripted at scale.
What Botnets Are Used For
Attackers use botnets' collective power for various malicious purposes:
DDoS attacks: Distributed Denial of Service attacks use the botnet to flood a target with traffic from all the compromised devices, overwhelming and taking down websites and services. This is a primary botnet use.
Spam: Botnets send massive volumes of spam email from the compromised devices, distributing the sending to evade blocking.
Credential stuffing and brute force: Botnets distribute these attacks across many devices, attempting account compromises at scale.
Cryptomining: Botnets use the compromised devices' resources to mine cryptocurrency for the attacker.
Malware distribution: Botnets spread malware further, growing themselves and infecting more victims.
Data theft: Compromised devices can be used to steal data from their owners and networks.
The collective power of many devices makes botnets capable of large-scale malicious operations.
Signs Your Device Might Be in a Botnet
A device in a botnet may show signs (though it may also show none):
- Slow performance and high resource usage
- Unusual network activity (the device communicating when idle)
- Overheating and high data usage
- Your IP being flagged for spam or malicious activity
- Security software detecting botnet malware
- Unexplained device behavior
IoT devices in botnets often show few obvious signs, making them particularly insidious.
How to Keep Your Devices Out of Botnets
The defenses against botnet conscription are the same as general malware defenses, with special attention to IoT devices:
Keep software updated: Patch vulnerabilities that botnet malware exploits. Keep your OS, software, and device firmware updated.
Secure IoT devices: IoT devices are prime botnet targets. Change default credentials on all IoT devices (a major botnet vulnerability), keep their firmware updated, and isolate them on a guest network. This is one of the most important botnet defenses, as poorly-secured IoT devices are conscripted at scale.
Use strong, unique passwords: Especially changing default passwords on all devices, since default credentials are a primary botnet entry point.
Use security software: Quality security software detects and blocks botnet malware.
Be cautious with downloads and email: Avoid the phishing and malicious downloads that deliver botnet malware.
Secure your network: A secure router and network prevent device compromise. Replace routers that no longer receive security updates.
Monitor your devices: Watch for signs of compromise, especially unusual network activity.
The IoT Botnet Problem
IoT devices deserve special attention regarding botnets:
Why IoT is targeted: IoT devices (cameras, smart home devices, routers) often have weak security — default credentials, unpatched vulnerabilities, and infrequent updates — making them easy to conscript at scale. Major botnets have been built largely from compromised IoT devices.
Securing IoT: Change default credentials, keep firmware updated, isolate IoT devices on a guest network, and disable unnecessary features. These steps prevent your IoT devices from being conscripted.
The scale issue: Because there are so many poorly-secured IoT devices, they enable large botnets. Securing your IoT devices contributes to reducing this problem.
Frequently Asked Questions
How do I know if my device is part of a botnet?
Signs include slow performance, high resource usage, unusual network activity (especially when idle), overheating, high data usage, and security software detecting botnet malware. Your IP might also be flagged for spam or malicious activity. However, botnet malware often runs quietly to avoid detection, and IoT devices in botnets may show few signs. Running security software and monitoring for unusual network activity help detect botnet infections.
Why are IoT devices such common botnet targets?
IoT devices (cameras, smart home devices, routers) often have weak security — default credentials, unpatched vulnerabilities, and infrequent updates — making them easy to conscript, and there are vast numbers of them. Major botnets have been built largely from compromised IoT devices. Securing your IoT devices — changing default credentials, updating firmware, and isolating them on a guest network — prevents them from being conscripted into botnets.
How do I keep my devices from being part of a botnet?
Use the same defenses as against malware generally, with special attention to IoT devices: keep all software and firmware updated, change default credentials on all devices (especially IoT), use strong unique passwords, use security software, be cautious with downloads and email, secure your network, and isolate IoT devices on a guest network. Since poorly-secured IoT devices are prime botnet targets, securing them is especially important.
Conclusion
A botnet is a network of malware-infected devices secretly controlled by an attacker to perform malicious actions collectively — from DDoS attacks and spam to credential stuffing, cryptomining, and malware distribution. Devices are conscripted through malware infection, with poorly-secured IoT devices being prime targets, easily compromised at scale through default credentials and unpatched vulnerabilities. Keeping your devices out of botnets uses the same defenses as against malware generally — updating software, using security software, and caution with downloads and email — with special attention to securing IoT devices by changing default credentials, updating firmware, and isolating them on a guest network. Since vast numbers of poorly-secured IoT devices enable large botnets, securing your IoT devices is particularly important, both protecting your devices and contributing to reducing the botnet problem. By understanding how botnets conscript devices and maintaining strong security, especially for IoT devices, you can keep your devices from becoming part of these malicious networks.