What Is a Botnet? 

A botnet, short for robot network, is a network of computers that have been infected with malware and are controlled remotely by an attacker known as the bot herder. Bot herders orchestrate mass attacks by leveraging compromised devices—bots—to capture sensitive information such as keystrokes and passwords. Bots are hijacked to simultaneously carry out multiple malicious activities, such as crashing networks, stealing data, and injecting more malware to perpetuate vulnerabilities further.

How Botnets Work

Botnet attacks typically execute the following actions:

Identify Vulnerabilities

Threat actors build botnets by finding website, application, or user behavior vulnerabilities. They exploit the security flaws within the software and deliver the malware through email and other online mediums. 

Infection

Threat actors employ social engineering tactics or use drive-by downloads to manipulate users into taking actions that result in their devices becoming infected and compromised by botnet malware. 

Activate

Each infected device is controlled and organized into a network of remotely managed bots. The bot herder’s command-and-control server acts as the central hub, providing instructions to the entire botnet. One of two control models is employed: 1) a centralized model involving direct communication between the bot herder and each compromised computer, or 2) a decentralized system with multiple links connecting all the infected botnet devices. 

Types of Botnet Attacks

Threat actors leverage botnets for various malicious activities:

DDoS attacks: In DDoS attacks, the botnet sends overwhelming requests to crash the targeted server or application. These attacks target organizations for personal or political motives or to extort payment in exchange for ceasing the attack. 

Email Spam and Phishing: Threat actors use email spam to distribute malware and deploy phishing campaigns to steal sensitive information, such as login credentials.

Information Theft: Many botnets enable attackers to steal sensitive data like credit card details or enterprise funds. 

Backdoor Intrusion: Threat actors employ smaller botnets to target and compromise specific high-value systems of organizations, enabling them to infiltrate the network and expand their intrusion. Backdoor intrusions are extremely dangerous, targeting valuable assets like financial data, research and development, intellectual property, and customer information. 

Systems Sabotage: Systems sabotage attacks infect targeted devices to prevent them from operating. The botnet attack uses malware to corrupt the devices and deletes all evidence of its presence, enabling the malware to remain undetected. 

Examples of Botent Operations

Botnets are typically the infiltration stage of a multi-layer scheme. They grow, automate, and accelerate the ability to carry out more significant attacks, such as these notable botnet operations: 

Zeus

Since 2007, the Zeus malware has infected its victims through phishing or spam emails and malicious downloads. Over the years, the evolution of this malware gave rise to various versions, leading to the GameOver Zeus bot in 2011, which infected around one million computers worldwide. 

Cutwail

In 2009, the Cutwail botnet was used in large-scale spam campaigns to exploit computer systems, targeting vulnerabilities such as outdated software and unpatched security flaws. During that time, it was responsible for up to 46.5% of the world’s total spam volume, sending out 51 million emails per minute, and was comprised of nearly 1.5 million bots.

Mirai

In 2016, the Mirai botnet attack targeted Dyn, a domain name system provider, resulting in widespread internet disruptions across the U.S. The attack involved over 100,000 malicious endpoints and was the first major botnet to infect IoT devices.

How to Prevent Botnet Attacks

Organizations can implement various cybersecurity practices to defend against and prevent botnet attacks.

1. Regular Software Updates

Botnets often exploit vulnerabilities in software that can be fixed with effective patch management. Regularly applying patches and updates to software, operating systems and devices is vital in mitigating botnet infiltration. 

2. Intrusion Detection and Prevention System

A Network Intrusion Detection and Prevention System (IDPS) monitors network traffic to identify and block suspicious activities. IDPS solutions use signature-based detection and anomaly-based detection techniques to enhance network security and protect against data breaches.

3. Endpoint Security

Deploying robust endpoint security solutions helps protect devices from various cyber threats, including botnet infection, by employing advanced threat detection techniques to detect and block malicious network traffic. 

4. Security Awareness Training

Regular security awareness training programs raise awareness about social engineering tactics that threat actors exploit. Educating employees on the best security practices is vital to preventing attacks and fostering a cyber-resilient culture.

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