What Is a Botnet? Definition, Types, and Protection In 2026

A botnet is a malicious network of infected devices that a cybercriminal controls from a remote location. Each infected device is called a bot or zombie computer because it follows commands quietly, without the owner knowing or agreeing.

In cybersecurity, a common botnet definition is:

A botnet is a distributed network of compromised systems infected by remote control malware and managed by a bot herder or botmaster through a command and control (C2).

The bot herder uses the C2 server to send instructions and to collect stolen data. The device owner may notice that the device is slower, see strange internet traffic, or see no clear signs at all.

How Do Botnets Work?

The botnet lifecycle usually has a few main steps. Attackers infect devices, connect them to a control system, spread to more devices, and then use the network for attacks or to make money.

Stage 1: Infection and Recruitment

Attackers always start by finding an infection vector, which is just their way to get a malware infection onto a device. They usually send phishing email messages with malicious attachments, fake installers, or links that open exploit kits in the browser. Those exploit kits look for security bugs in the browser or its plugins and can trigger a drive-by download, so the malware installs just because someone visits a risky page.

They also try to log in straight to exposed systems. To do that, they run brute force attacks and credential stuffing against weak admin passwords on routers, servers, cloud dashboards, and remote desktop gateways. When they manage to guess or reuse a valid password, they install remote control malware and quietly move that device into the botnet, where it starts following the attacker’s commands.

Stage 2: Command and Control

After the device is compromised, the malware connects back to the C&C server the command and control (C2) system that runs the entire botnet. This might be a single server or a cluster of servers managed by the botmaster. The traffic may look like normal web browsing, or it may be encrypted C2 traffic over HTTPS or other encryption protocols, which makes it harder for security tools to inspect.

Older IRC-based botnets used chat channels to send commands to bots. Modern HTTP-based botnets blend in with normal web traffic and use tricks such as DNS communication, domain generation algorithms (DGA), and fast flux DNS. These tricks keep changing domain names and IP addresses, so defenders find it hard to block all of them.

Stage 3: Propagation and Lateral Movement

Many botnet families  include a propagation mechanism, which is the part of the malware that spreads itself. After the first device is infected, the bot scans the local network and sometimes the wider internet. It looks for outdated software, weak passwords, or open admin pages. When it finds another easy target, it infects that system and adds it to the botnet.

Inside an organization, this is called lateral movement. The attacker moves from a user’s laptop to file servers, databases, and cloud services step by step. The botnet can then send new modules or updated malware to all the infected devices it already controls.

Stage 4: Attack and Persistence

At any time, the botmaster can send commands to the bots to start an operation. This can mean a Distributed Denial of Service (DDoS) attack that floods a site with traffic, a large phishing campaign, ransomware delivery, or slow data exfiltration where sensitive data is quietly sent out of the network over time.

Modern botnets are built for resilience. They can switch to backup C2 servers if one is blocked, use traffic obfuscation to hide patterns in their network traffic, and update themselves automatically. They also use anti-analysis tricks to confuse antivirus tools and malware analysis, which makes the botnet harder to detect and remove.

What Do Botnets Do?

A botnet is a flexible tool for cybercrime. The same malicious network can be reused for different jobs over time, depending on what the operator wants to achieve.

DDoS and Large-Scale Disruption

The most common botnet attack is a Distributed Denial of Service (DDoS) attack. In this attack, the botmaster tells thousands of infected devices to send traffic to the same target at the same time. In a volumetric attack, the goal is simply to flood the target’s internet connection.

In an application-layer attack, the bots keep calling specific pages or APIs until the site or app becomes too slow for real users. In a SYN flood and similar protocol attacks, the bots start lots of fake TCP connections so the server runs out of capacity for real ones.

Some DDoS botnets use IoT devices and DNS amplification to make the traffic even larger. Recent reports say DDoS attacks grew by about 82% in 2024 and that each attack cost businesses around 234,000 dollars on average. Another report described a record DDoS attack of about 15.7 terabits per second, launched by hundreds of thousands of hacked IoT devices against a single cloud provider.

Spam, Phishing, and Malware Delivery

Spam botnets send huge numbers of unwanted emails. These messages might promote scams, advertise fake products, or include malicious attachments and links that silently install new malware when opened pulling the victim’s device into the botnet.

When they work together with ransomware botnets, a single wave of phishing emails can infect many devices at once, which then download ransomware or other harmful files and give attackers a way into the network.

Credential Theft and Account Takeover

Many banking botnets and similar malware can log keystrokes, hook into browsers, and steal cookies. This helps attackers capture logins for banking websites, email accounts, and cloud admin portals.

At the same time, they use the botnet to run brute force login attacks and credential stuffing, trying large lists of leaked passwords across many different services. When one works, they get account takeover without ever talking to the real user.

Financial Fraud, Click Fraud, and Ad Fraud

Families such as Necurs are used for click fraud and ad fraud. In these campaigns, bots pretend to view ads, click on them, or install apps. This turns stolen computing power into money and helps cybercriminals move funds through fake advertising networks and traffic markets.

Crypto Mining and Proxy Services

Crypto mining botnets install mining software on CPUs, GPUs, and sometimes on IoT devices. This hidden mining uses a lot of processing power, so systems slow down, fans run harder, devices may overheat, and power bills go up without a clear reason.

Other groups run proxy botnets. They sell access on dark web marketplaces so other cybercriminals can send their traffic through infected devices. This makes the traffic look like it is coming from normal users and helps hide where the attacks really start.

Botnet Architecture Explained

Botnet architecture is the way the bots and controllers are designed, connected, and managed. Whether centralized or peer-to-peer, every botnet is fundamentally a distributed network its power comes from spreading control and activity across thousands of devices simultaneously

Centralized Botnets

In a centralized botnet, one or a few main C2 servers control the whole network. This is the simplest and oldest botnet structure easy for attackers to manage but also easier for defenders to disrupt by targeting the C&C server.

Every bot connects to these servers to get commands and send back results. Cybercriminals usually host these servers with bulletproof hosting providers that ignore or delay abuse reports. They may also send traffic through the TOR network or other proxies to hide where they really are.

This setup is simple for attackers to run, but it has a clear weak point. If investigators or law enforcement find and shut down the C2 servers, they can usually break most of the botnet in one step. Because of this, many botnet disruption operations focus on taking over or sinkholing the domains that bots use to reach their controllers.

Peer-to-Peer and Hybrid Botnets

In a peer-to-peer (P2P) botnet or decentralized botnet, bots do not depend on a single central server. Each bot uses P2P communication to talk directly to other bots and pass commands along the network meaning there is no single point of failure that defenders can target to shut everything down.

The real controller may only need to reach a small group of infected devices, and those devices spread the instructions to the rest.

Many advanced families use hybrid botnets. A small, hidden central layer sets the overall plan, and a P2P layer handles everyday sharing of commands and updates. This structure is harder to shut down, because there is no single C2 system that will disable the whole botnet if it is removed.

Cloud and IoT-Centric Designs

Modern botnets now target far more than just home and office computers. Cloud botnets and cloud-native botnets go after virtual machines, containers, and serverless services that run in cloud platforms. IoT botnets build huge networks from routers, IP cameras, smart TVs, and other smart home or industrial devices that usually have weak security by default.

Attackers also focus on edge device exploitation and new 5G botnet threats as more work moves to mobile networks, edge servers, and gateways. Analysts expect the number of connected IoT devices to reach about 21.1 billion by the end of 2025, which gives cybercriminals a constantly growing pool of devices that can be turned into bots.

Types of Botnets and Platforms

Regardless of platform or purpose, every bot in the network is essentially one of millions of zombie computers silently waiting for the bot master’s next command.

By platform, there are Windows botnets and Linux botnets, IoT botnets made from smart devices, mobile botnets built from phones and tablets, and cloud botnets that run in public cloud environments. By communication method, you see IRC-based botnets (the earliest model, now mostly retired), HTTP-based botnets that blend with normal web traffic, P2P botnets with no central control point, and hybrid designs that mix these approaches.

Attackers also build botnets for specific jobs.

• DDoS botnets focus on large traffic floods. 
• Spam botnets send bulk email and support phishing attacks. 
• Banking botnets and banking trojans target online banking users and carry out financial fraud. 
• Crypto mining botnets install hidden miners on CPUs and GPUs to generate cryptocurrency. 
• Proxy botnets turn infected devices into rented anonymizing relays that other cybercriminals can use to hide where their traffic really comes from.

Real-World Botnet Examples

Mirai

Mirai is a well-known IoT botnet. It scanned the internet for devices with default or weak passwords, mainly cameras and routers. Once it infected them, it used those devices to launch huge DDoS attacks, including the Dyn DNS attack in 2016 that interrupted access to many popular websites at the same time.

Zeus and GameOver Zeus

Zeus was a major banking Trojan/malware family used to build botnets, which infected millions of Windows systems. It focused on credential harvesting for online banking. GameOver Zeus was a later P2P botnet version that used decentralized control, which made it harder to shut down. It was also used to deliver CryptoLocker ransomware.

Emotet

Emotet started as a banking trojan and later became a flexible loader and ransomware botnet. It spread mainly through spam and phishing email campaigns. After it infected a system, it downloaded and installed other malware families, including several ransomware strains. This caused serious damage in many networks.

Necurs

Necurs became one of the largest spam botnets ever recorded. It sent bulk email, promoted fake pharmaceuticals, and distributed several types of malware. It is often used as a classic example of a spam focused malware network.

How to Detect Botnet Traffic

Detecting botnet traffic is hard, because the malware tries to look like normal use of the internet. Techniques like domain generation algorithm (DGA) and fast flux DNS make detection even harder bots constantly cycle through new domains, so simple blocklist-based defenses quickly fall behind. A good approach checks devices, the network, and outside threat data together.

Watch Your Endpoints

Use endpoint detection and response (EDR) or modern endpoint security on your laptops and servers. These tools should flag strange programs that keep talking to unknown or risky domains, try to stay on the system after restart, or try to turn off security tools or skip sandbox analysis.

Monitor Network Traffic Closely

Use firewall monitoring, network traffic analysis, intrusion detection systems (IDS), and intrusion prevention systems (IPS). Look for sudden jumps in outbound traffic and connections to unusual places on the internet. Also watch for unusual DNS communication patterns rapid domain lookups, unusually short TTL records, or connections to newly registered domains are common signs of botnet C2 activity. Anomaly detection and behavioral analysis help you spot devices that behave like bots, even when the C2 traffic is encrypted.

Add Threat Intelligence To Your View

Connect your tools to threat intelligence feeds so they know about known bad IP addresses, domains, and command and control servers. This makes it easier to see when local traffic matches known botnet traffic patterns instead of treating each alert in isolation.

Use Honeypots For Real-World Insight

Security teams and researchers often set up honeypots, which are fake systems placed on the internet to attract bots and scanners. These systems collect real attack data. That data then feeds into botnet tracking projects and helps improve your own threat mitigation and detection rules.

Emerging Botnet Trends in 2026

Botnets are changing all the time, just like the rest of the internet. AI-powered botnets now use machine learning to change how they behave, pick new targets, and avoid simple detection rules. Traditional exploit kit based infections are also being upgraded with AI-generated lures, making them harder to distinguish from legitimate content.

There are also botnet-as-a-service (BaaS) platforms, where cybercriminals can rent DDoS, spam, or account takeover tools instead of building their own botnet.

With the growth of 5G and edge computing, it is easier to abuse devices at the edge of the network. Large numbers of smart cameras, industrial sensors, and other IoT devices with weak smart home security are being pulled into bigger IoT botnets and stronger IoT DDoS attacks.

Inside large companies, defenders now watch for supply chain botnet infections, where attackers tamper with software updates or build tools, and for cloud-native botnets that live only in cloud platforms. Some groups run API abuse botnets that keep attacking login and payment APIs. Others use deepfake phishing and AI tools to create very realistic scam emails, messages, and voice calls.

Botnet Protection and Prevention

Good botnet protection strategies start with basic computer virus prevention measures and then add stronger layers of defense.

Reduce the Attack Surface

The first step in botnet protection is making sure your infected devices risk stays low. Unpatched systems and default-password IoT gear are the most common entry points. This includes routers, VPN gateways, and IoT devices such as cameras and smart TVs. Strong patch management and regular firmware updates close known holes that attackers like to use.

For IoT and smart home devices, change default passwords as soon as you set them up. Turn off features you do not need, and do not expose admin pages directly to the internet. This makes it much harder for a botnet to recruit those devices.

Strengthen Accounts and Identity

Use strong, unique passwords and store them in a password manager. Turn on multi-factor authentication (MFA) for important accounts and admin portals. This makes brute force attacks and credential stuffing far less effective, even when attackers have large lists of leaked passwords.

Support this with security awareness training so people recognize phishing emails and fake login pages the most common triggers of malware infection that pulls a device into a botnet.

Harden Networks and Segment Systems

A zero trust architecture (ZTA) treats every connection as untrusted until it is checked. When you combine this with network segmentation, you limit how far an infection can spread if one device is compromised. Important systems should live on separate network segments with strict access rules.

At the same time, deploy IDS/IPS, next generation firewalls, and AI-based threat detection to find and block connections to known C2 domains and suspicious traffic patterns. EDR and digital forensics tools help investigate incidents, remove malware, and confirm that infected hosts are clean.

Prepare to Respond and Investigate

Create clear steps for handling suspected botnet activity. These steps should cover isolating affected devices, collecting logs, keeping evidence for digital forensics, and planning recovery. For serious cases, support from a security operations center or an external incident response team can help contain and fix the problem more quickly.

Final Thoughts

A botnet is a practical way for attackers to turn many small weaknesses into one big problem. The same basic habits that protect you from normal malware also lower your risk from these networks. Keep software updated, protect accounts, secure your network, and watch for unusual activity.

If you treat every device as something that might be abused and every connection as something that should be checked, you make it much harder for a bot herder to recruit your systems into their next malicious network.

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