A botnet is a network of compromised computers or devices, often referred to as “zombies” or “bots,” that are controlled bya malicious actor known as a “botmaster” or “bot herder.” The devices in a botnet can include personal computers, servers, mobile devices, and even Internet of Things (IoT) devices like smart cameras, routers, and appliances.

Cybercriminals create botnets by infecting large numbers of devices with malware, which allows them to remotely control the devices without the knowledge
or consent of their owners. This malware can spread through various means, such as phishing emails, malicious websites, or unpatched software vulnerabilities. Once a device is compromised and becomes part of a botnet, the botmaster can use it to carry out a variety of malicious activities.

Types of Botnet

IRC Botnets

IRC (Internet Relay Chat) botnets are one of the earliest types of botnets, utilizing IRC servers for command and control (C&C) communication between the botmaster and the compromised devices. IRC is a protocol that facilitates real-time text messaging, making it an ideal platform for controlling botnets. The botmaster can issue commands to the bots through specific IRC channels, instructing them to perform various malicious activities.

One example of an IRC botnet is Agobot, a modular botnet that has been used for DDoS attacks, keylogging, and data theft. Agobot’ssource code was leaked in 2004, leading to the development of numerous variants and inspiring the creation of other IRC botnets. The modular nature of Agobot allows botmasters to easily add or remove functionalities, making it highly adaptable to different malicious purposes.

HTTP Botnets

As cybersecurity measures evolved, botnet operators shifted towards using HTTP or HTTPS protocols for C&C communication. HTTP botnets are harder to detect and block because they blend in with legitimate web traffic. Botmasters can create web-based control panels to manage their bots, issue commands, and monitor their activities.

The Zeus botnet, also known as Zbot, is a notorious example of an HTTP botnet. Zeus is primarily designed to steal banking credentials and other sensitive information from infected computers. It uses techniques like keystroke logging and form grabbing to capture user input and send it back to the botmaster. The Zeus botnet has been responsible for significant financial losses worldwide, with some estimates suggesting that it has caused damages exceeding $100 million

P2P Botnets

Peer-to-Peer (P2P) botnets have emerged as a more resilient alternative to centralized botnets. In a P2P botnet, there is no central C&C server; instead, the bots communicate directly with each other, forming a decentralized network. This architecture makes P2P botnets more difficult to take down, as there is no single point of failure. Even if some bots are discovered and removed, the remaining bots can continue to operate and maintain the botnet’s functionality.

The Storm botnet is a prime example of a P2P botnet that has caused significant damage. It uses the Overnet P2P protocol for C&C communication and has been used for various malicious activities, including spam email campaigns and DDoS attacks. At its peak, the Storm botnet was estimated to have infected millions of computers worldwide, making it one of the largest botnets ever created.

Mobile Botnets

With the proliferation of mobile devices, such as smartphones and tablets, botnet operators have started targeting these devices to expand their botnets. Mobile botnets often spread via malicious apps or SMS messages, exploiting vulnerabilities in mobile operating systems or tricking users into installing malware.

The Chamois botnet is an example of an Android botnet that has infected millions of devices worldwide. Chamois uses infected devices for ad fraud, generating fake clicks on advertisements to earn money for the botmasters. It also has the capability to install additional malware on the compromised devices, further
expanding its malicious potential.

IoT Botnets

IoT has introduced a new attack surface for botnet operators. IoT devices, such as smart cameras, routers, and home appliances, often have weak security measures and default credentials, making them easy targets for compromise. Once infected, these devices can be used to carry out DDoS attacks, mine cryptocurrencies, or spread malware to other devices.

The Mirai botnet is a notorious example of an IoT botnet that has caused significant disruption. Mirai targets IoT devices with default or weak credentials, infecting them and using them to carry out largescale DDoS attacks. In 2016, the Mirai botnet was used to launch a massive DDoS attack against the DNS provider Dyn, causing widespread internet outages and affecting major websites like Twitter, Netflix, and Reddit.

How to mitigate Botnet attacks?

Mitigating the threat posed by botnets requires a multi-faceted approach because there is no one-size-fits-all solution. The specific strategies and tools used will depend on the type of attack being carried out by the botnet and the unique characteristics of the affected organization or individual.

Firewall and intrusion prevention systems, advanced email filtering and anti data exfiltration solutions are among the ways to mitigate the risk and impact of botnet attacks on your organization.