What is a botnet and how is it used?

What is a botnet? Definition, how it works and how to prevent an attack

A botnet is a network of computers infected with malware, often controlled remotely by cybercriminals. These compromised devices, also called zombies or bots, are used to carry out a variety of malicious activities, including DDoS attacks, data theft, malware distribution and cryptocurrency mining. Botnets can range in size from a handful of devices to millions of infected systems across the globe.

Botnet definition

The term “botnet” is short for “robot network” and refers to a group of computers, servers or IoT devices infected with malware and controlled by cyber criminals, also known as bot herders or botnet operators. These individuals or groups use botnets to carry out large-scale cyberattacks, often driven by financial motives or a desire for recognition in hacker communities. Botnets operate through either a centralized command and control (C2) server or a decentralized peer-to-peer (P2P) system.

Most victims remain unaware that their devices have been compromised. Once infected, the device continues to function normally on the surface while quietly executing commands in the background. Infected computers within a botnet are orchestrated to perform attacks, following instructions from the command and control server.

Common uses of botnets include:

• Launching distributed denial-of-service (DDoS) attacks

• Stealing sensitive data and login credentials

• Spreading malware

• Sending spam and phishing emails

• Mining cryptocurrency using hijacked processing power

Types of botnets

Botnets vary in structure and purpose. Some are designed specifically for DDoS attacks, while others are more advanced and can distribute different types of malware. The two primary types are:

• Centralized botnets, where all infected devices connect to a single command and control server

• Decentralized (P2P) botnets, where commands are distributed between devices without a central controller

Understanding these structures is essential for identifying threats and defending against them. Botnets are used in various attack types, including phishing schemes and account takeovers, demonstrating the scale and versatility of these threats. Different types of botnet attacks include DDoS attacks, phishing schemes, and account takeovers, which leverage botnets to operate on a larger scale and achieve various goals.

Botnet lifecycle

The lifecycle of a botnet encompasses several stages, from its inception to its potential dismantling. It begins with the initial infection of a device, often through malicious software delivered via phishing emails, compromised websites, or unpatched vulnerabilities. Once a device is infected, it becomes part of the botnet, and the bot herder can start recruiting additional devices to expand the network.

As the botnet grows, it enters a phase of expansion, increasing its reach and capabilities. During this period, the botnet may be used to conduct various types of attacks, such as DDoS attacks, spamming, and data theft. The bot herder continuously seeks to enhance the botnet’s sophistication, making it more resilient and harder to detect.

However, as the botnet becomes more prominent, it may attract the attention of law enforcement and cybersecurity professionals. Efforts to disrupt or shut down the botnet involve a combination of technical measures, such as isolating and cleaning infected devices, and legal actions against the operators. Despite these efforts, some botnets manage to evolve and adapt, continuing to operate and evade detection.

How a botnet works

Infection through malware

Cybercriminals typically spread botnet malware through various methods, leading to malware infection. These methods include phishing emails, malicious websites, unpatched software vulnerabilities, or drive-by downloads. Once the malware is installed, it connects the device to the botnet and remains hidden to ensure continued access.

Botnet drones (zombie computers)

When a device is infected, it becomes a botnet drone or zombie. These bots may act independently or await commands from the bot herder. Common targets for infection include:

• Personal computers and laptops

• Smartphones and tablets

• IoT devices such as smart TVs, routers and security cameras

IoT devices are especially vulnerable due to weak security configurations, including the use of default passwords and lack of regular updates.

Command and control (C2) systems and bot herders

Bot herders control infected devices through command and control systems. While older botnets used centralized C2 servers, modern botnets often rely on peer-to-peer communication, making them more resilient and harder to shut down.

Common C2 communication methods include:

• IRC (Internet Relay Chat)

• HTTP/HTTPS

• Telnet

• social platforms like Twitter and GitHub

Targeting specific points of failure in the command and control infrastructure can disable the entire botnet.

What are botnets used for?

DDoS attacks

Botnets are widely known for powering DDoS attacks. In this type of attack, thousands of devices send traffic to a single target, overwhelming it and forcing it offline. Read more about how DDoS attacks work in our in-depth article.

Cryptocurrency mining

Botnets can use the processing power of infected devices to mine cryptocurrencies such as Bitcoin or Monero. This often occurs without the user noticing.

Malware delivery

Botnets are used to download and install additional malware, such as ransomware, trojans or spyware. Learn more about what malware is and how it works in our detailed guide.

Spam and phishing campaigns

Cybercriminals use botnets to send massive volumes of spam and phishing emails, aiming to infect even more devices or steal sensitive information.

Credential theft and surveillance

Advanced botnets can log keystrokes, monitor user activity or steal login credentials. Read more about what credentials are and why they matter in cybersecurity.

Common botnet attack methods

Botnets enable a wide range of attacks:

• DDoS attacks: Overwhelm targets with traffic to take services offline

• Malware distribution: Deliver ransomware, trojans, or spyware

• Phishing scams: Send fake emails to trick users into sharing sensitive data

• Spam: Flood inboxes with unsolicited messages

• Ad fraud: Generate false ad clicks to earn revenue

• Data theft: Steal personal and financial information

• Ransomware: Lock data and demand payment for access

Why hackers use botnets

Botnets are attractive to hackers for several reasons:

• Anonymity: Attacks are routed through compromised devices, masking the origin

• Scalability: Large botnets can carry out massive attacks

• Versatility: A single botnet can support many types of malicious activity

• Profitability: Botnets generate income through ransomware, ad fraud or selling stolen data

• Accessibility: Tools to build and manage botnets are readily available on the dark web

Real-world botnet examples

Mirai

Mirai infected poorly secured IoT devices and launched a major DDoS attack in 2016, taking down major services like Twitter and Netflix.

TrickBot

Originally a banking trojan, TrickBot evolved into a modular botnet capable of delivering other malware, including ransomware.

Khan C. Smith's spam botnet

In 2001, this botnet was used to send mass spam emails and generated millions of dollars. Its operator was eventually sued by EarthLink.

Impact of botnets on businesses and individuals

Botnet attacks can have devastating effects on both businesses and individuals. For businesses, the consequences can include significant financial losses, reputational damage, and compromised sensitive information. DDoS attacks, for instance, can lead to prolonged downtime, lost productivity, and revenue losses as services are rendered unavailable.

Individuals are not immune to the impact of botnets either. Personal data can be stolen, leading to identity theft or financial fraud. Infected devices may be used to spread malware, causing further harm and potentially compromising additional systems. Phishing scams conducted through botnets can trick individuals into revealing sensitive information or installing malicious software on their devices.

The ripple effects of botnet attacks extend beyond the immediate victims, affecting the broader online community. The widespread nature of these attacks underscores the importance of robust cybersecurity measures to protect against the far-reaching impact of botnets.

Signs of a botnet infection

While botnet malware is designed to be stealthy, these symptoms may indicate a compromised device:

• Unusual internet activity when idle

• Unexplained system slowdowns

• Frequent crashes

• Disabled antivirus or firewall settings

• Strange outbound network traffic

Botnet detection techniques

Detecting botnets requires a multifaceted approach that combines technical and analytical techniques. One common method is to monitor network traffic for suspicious patterns or anomalies that may indicate botnet activity. Unusual spikes in traffic, unexpected outbound connections, and irregular data flows can all be signs of a botnet at work.

Machine learning algorithms are increasingly being used to analyze device behavior and identify potential botnet activity. These algorithms can detect subtle changes in behavior that may not be immediately apparent through traditional monitoring techniques.

Honeypots, which are decoy devices or systems designed to attract and detect botnet activity, are another valuable tool in the cybersecurity arsenal. By luring botnets into interacting with these decoys, cybersecurity professionals can gain insights into the botnet’s behavior and tactics.

Botnet detection tools may employ signature-based detection, behavioral analysis, or anomaly-based detection to identify potential threats. Keeping software and systems up to date, using antivirus software, and enabling firewalls are also crucial steps in preventing botnet infections.

How to prevent or stop a botnet attack

Protect your devices

• Avoid clicking unknown links or opening suspicious attachments

• Use strong, unique passwords

• Keep software and firmware updated

• Install and regularly update antivirus software

• Monitor outbound traffic for unusual patterns

Defend against attacks

• Use a content delivery network (CDN) to handle DDoS traffic

• Invest in DDoS protection services

• Block known malicious IP addresses

• Analyze network traffic for signs of command and control activity

Prevention strategies

To reduce the risk of botnet attacks:

• Update all devices regularly, especially IoT hardware

• Use antivirus software and enable real-time scanning

• Enable firewalls and configure them to block suspicious activity

• Avoid phishing emails and unverified downloads

• Create strong passwords and use a password manager

• Monitor network traffic to identify irregularities

• Apply ingress and egress filtering to control data flow

• Use botnet detection tools to identify infected systems

Legal and ethical implications of botnets

Botnets raise significant legal and ethical concerns, as they often involve the unauthorized use of devices and the theft of sensitive information. Creating or operating a botnet is typically considered a cybercrime, punishable by law in many jurisdictions. However, the legal framework surrounding botnets is still evolving, and there may be gray areas or uncertainties in certain cases.

From an ethical perspective, botnets raise concerns about privacy, security, and the responsible use of technology. Cybersecurity professionals and individuals must consider the ethical implications of their actions when dealing with botnets, including the potential consequences of disrupting or shutting down a botnet. There may also be ethical considerations around the use of botnets for legitimate purposes, such as research or testing.

Navigating the legal and ethical landscape of botnets requires a careful balance between protecting against cyber threats and respecting the rights and privacy of individuals.

Emerging trends in botnet technology

Botnet technology is constantly evolving, with new trends and techniques emerging regularly. One notable trend is the use of artificial intelligence (AI) and machine learning (ML) to create more sophisticated and adaptive botnets. These advanced botnets can learn from their environment and adjust their tactics to evade detection and improve their effectiveness.

The proliferation of Internet of Things (IoT) devices has also provided a large pool of potential devices to infect, making IoT botnets a growing concern. These devices often have weak security configurations, making them easy targets for bot herders.

Decentralized botnets, which rely on peer-to-peer communication rather than a central command and control server, are becoming more prevalent. These botnets are more resilient and harder to disrupt, posing a significant challenge for cybersecurity professionals.

Additionally, the use of blockchain technology and cryptocurrencies is becoming more common in the botnet ecosystem. These technologies can make it harder to track and disrupt botnet operations, as they provide a level of anonymity and decentralization.

To effectively prevent botnet attacks, cybersecurity professionals must stay up to date with the latest trends and techniques in botnet technology. This ongoing vigilance is essential to protect against the ever-evolving threat landscape.

How to disable a botnet

Neutralizing a botnet involves:

• Identifying infected systems

• Isolating and cleaning those devices

• Disrupting the command and control infrastructure

• Working with cybersecurity professionals or law enforcement for large-scale cases

Summary

Botnets are among the most powerful and persistent threats in cybersecurity. They can disrupt services, steal data, spread malware and generate profit for cybercriminals. Fortunately, many botnet attacks can be prevented by following good security practices and staying alert to suspicious activity. By protecting your devices and networks, you help defend against this widespread digital threat.