What Is a Botnet? How Attackers Exploit Malware

Once a device is part of a botnet, it can be remotely controlled by an attacker known as a bot herder who issues commands to launch DDoS attacks, steal credentials, and spread malware — often without the owner's knowledge. These networks can range from hundreds to millions of infected devices, allowing cybercriminals to scale their operations with minimal effort.

How do botnets work? Discover how they spread and exploit devices

Botnets follow a three-stage lifecycle: infection, command and control, and exploitation.

1. Infection: How devices become bots

Cybercriminals use various techniques to compromise systems and expand their botnet:

• Phishing Emails – Malicious attachments or links install botnet malware.
• Software Vulnerability Exploits – Hackers target unpatched operating systems, applications, and IoT devices.
• Drive-By Downloads – Malware is installed when users visit infected websites.
• Brute-Force Attacks – Automated tools guess weak passwords to gain system access.

Once infected, the device operates silently in the background, awaiting further instructions from the bot herder.

2. Command and Control (C2) Systems

After infection, bots connect to a command-and-control (C2) server, where attackers issue commands and collect stolen data. The two main C2 structures include:

• Client-Server Model – Bots connect to a centralized C2 server, making management efficient but vulnerable to takedown efforts.
• Peer-to-peer (P2P) Model – Bots communicate with each other rather than a central server, making the botnet more difficult to disrupt.

3. Exploitation: How Attackers Use Botnets

Once established, botnets are used for a range of cybercriminal activities:

• DDoS Attacks – Overload websites or networks with traffic to shut them down
• Credential Theft – Logging keystrokes or stealing saved passwords for financial fraud
• Cryptojacking – Using infected devices to mine cryptocurrency without the owner’s consent
• Click Fraud – Generating fake ad clicks to steal revenue from advertisers
• Spam and Phishing Campaigns – Sending mass phishing emails to expand infections

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The lifecycle of a botnet: From creation to takedown

Botnets don’t emerge overnight—they follow a lifecycle that enables them to grow, operate, and sometimes evade takedown attempts.

1. Creation and Deployment

• Cybercriminals develop or purchase botnet malware on dark web marketplaces.
• The malware is embedded in phishing emails, malicious ads, or exploit kits.

2. Recruitment and Growth

• Users unknowingly download malware, turning their devices into bots.
• The botnet spreads through self-propagating techniques like worm-like replication.

3. Exploitation and Monetization

• Attackers use infected devices for DDoS attacks, spam campaigns, data theft, and cryptojacking.
• Some botnets are rented out as Botnet-as-a-Service (BaaS) for profit.

4. Detection and Law Enforcement Response

• Security researchers and law enforcement track C2 servers, bot activity, and malware signatures.
• Attempts are made to disrupt botnet operations by blocking command channels.

5. Takedown Attempts and Resurgence

• Authorities seize botnet infrastructure and domains to cut off attacker control.
• Cybercriminals quickly rebuild botnets using new infrastructure and malware variants.

Despite takedown efforts, botnets often resurface in new forms, evolving to evade detection and exploit emerging vulnerabilities.

How botnets stay undetected: Advanced evasion techniques

Modern botnets use sophisticated techniques to remain invisible to security tools. These techniques make them harder to detect and remove.

1. Encryption and Obfuscation

• Botnets encrypt C2 communications to hide traffic from security tools.
• Some use domain fluxing, which rapidly changes their C2 server locations.

2. Fileless Malware

• Some botnets run entirely in memory, leaving no files on disk for antivirus programs to detect.

3. Fast-Flux Networks

• Bots frequently switch IP addresses, making it difficult for security teams to block C2 traffic.

4. Sleeping Botnets

• Some bots remain dormant for long periods before activating, evading detection.

5. Peer-to-Peer (P2P) Communication

• Decentralized botnets avoid using a single C2 server, making takedowns much harder.

These evasion techniques make botnets a persistent cybersecurity threat.

How to identify if your device is part of a botnet

Many users don’t realize their devices are infected. Here are the top warning signs to look for:

1. Unusual Network Activity

• Unexpected spikes in outgoing data traffic could mean your device is communicating with a C2 server.

2. Slow Device Performance

• If your computer, phone, or IoT device is sluggish for no reason, it may be running hidden botnet operations like cryptojacking.

3. Frequent Captchas on Websites

• If you constantly see captchas while browsing, your IP may be flagged for suspicious botnet activity.

4. Unexpected Outgoing Emails or Messages

• A botnet might be using your device to send spam or phishing messages to others.

5. Connections to Suspicious IPs

• Your firewall or network monitoring tools may detect connections to known botnet-related domains.

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How bot herders control malware

A bot herder is the cybercriminal managing the botnet, ensuring it remains operational and profitable while avoiding detection.

Command and Control Mechanisms

Bot herders maintain control through C2 infrastructure, which allows them to:

• Send attack commands to infected bots.
• Distribute malware updates to enhance functionality.
• Collect stolen data and relay it to criminal networks.

To avoid detection, many botnets use encryption, domain-fluxing (rapid domain changes), and fast-flux DNS techniques to keep C2 infrastructure hidden.

How Attackers Profit from Botnets

Botnets generate revenue in several ways:

• Selling Access ("Botnet-as-a-Service") – Renting infected devices to cybercriminals
• Ransomware Deployment – Encrypting victim files and demanding payment
• Financial Fraud – Stealing banking credentials and executing unauthorized transactions
• Cryptocurrency Mining – Using infected devices to generate cryptocurrency for attackers

Evasion and Persistence Techniques

Bot herders use advanced methods to ensure continued operation, including:

• Polymorphic Malware – Constantly changing code to bypass antivirus detection.
• Encrypted C2 Communication – Masking commands to avoid security tools.
• P2P Networks – Preventing centralized takedowns by distributing control across multiple infected machines.

Active botnets

While some botnets have been dismantled, many continue to evolve and pose threats today. Recent examples include:

Dridex – A Persistent Banking Trojan

Dridex spreads via phishing emails and is used for financial fraud, credential theft, and ransomware deployment. It continuously adapts, making it difficult to detect and remove.

Emotet – A Resilient Malware Distributor

Emotet is one of the most advanced malware delivery botnets, distributing ransomware and credential stealers. Despite takedown attempts, it frequently resurfaces with improved capabilities.

Mirai – The Leading IoT Botnet

Mirai infects IoT devices with weak passwords, turning them into tools for large-scale DDoS attacks. Numerous variants continue to target routers, cameras, and smart home devices.

Gorilla – An Emerging Cloud and IoT Threat

Gorilla is a recently identified botnet that has launched hundreds of thousands of DDoS attack commands worldwide, focusing on cloud-based infrastructure and IoT devices.

Necurs – A Dormant but Dangerous Threat

Necurs is a modular botnet used for spam campaigns, financial fraud, and malware distribution. It has been linked to banking trojans like Dridex and Locky ransomware. While it has remained relatively inactive in recent years, it has the potential to resurface.

Mantis – The Next-Generation DDoS Botnet

First discovered in 2022, Mantis is a highly efficient botnet capable of launching record-breaking DDoS attacks with fewer infected machines than previous botnets. It uses advanced techniques to amplify attack traffic, making it a major threat to businesses and cloud infrastructure.

Notable Disabled Botnets

While inactive, the following botnets shaped modern cyber threats:

• ZeuS (Zbot) – A banking trojan responsible for millions in financial fraud
• GameOver Zeus – A resilient, decentralized version of ZeuS
• Cutwail – A spam botnet that sent billions of fraudulent emails
• Storm – One of the first dark web rental botnets
• ZeroAccess – A botnet used for click fraud and cryptojacking
• 3ve – A sophisticated ad fraud botnet that cost advertisers millions of dollars

How to detect and prevent botnet attacks

Key Prevention Strategies

To reduce botnet risk, organizations should:

• Keep Software Updated – Regularly patch operating systems, applications, and IoT devices.
• Use Multi-Factor Authentication (MFA) – Prevent credential stuffing attacks.
• Deploy Network Segmentation – Restrict infected systems from communicating laterally.
• Monitor Threat Intelligence Feeds – Block known botnet domains.
• Implement AI-Powered Security – Use behavior-based detection to spot botnet activity.

How to Remove a Botnet Infection

If a botnet is detected:

• Isolate the Infected System – Disconnect it from the network to prevent spread.
• Block C2 Communications – Prevent outbound connections to botnet servers.
• Use Advanced Threat Detection – AI-driven tools can identify and eliminate malware.
• ‍Reset Compromised Credentials – Change passwords and enforce security policies.