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Botnet

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A botnet is a logical collection of Internet-connected devices. These devices can be computers, smartphones, or Internet of Things (IoT) devices. A botnet forms when the security of these devices is breached. Control is then ceded to a third party. Each compromised device is known as a "bot." The word "botnet" is a portmanteau of the words "robot" and "network." Most people use the term with a negative or malicious connotation.

Server-based-network
Server-based-network

To create a botnet, an originator must first infect devices with malware. This is malicious software designed to cause harm. A hacker might use a Trojan or an exploit kit to start this process. They may lure a user into a drive-by download. They might also exploit web browser vulnerabilities. Another common method is tricking a user into running a Trojan horse via an email attachment. Once the malware is installed, it installs modules. These modules allow the device to be commanded and controlled remotely. The infected computer is often called a "zombie computer." This name is a metaphor because the owner is usually unaware of the intrusion.

CIAJMK1209-en
CIAJMK1209-en

The person in charge of the botnet is called a bot herder or bot master. They manage the group through command and control, often called C&C. The herder uses a covert channel to send instructions to the bots. This process is sometimes called "scrumping," which refers to stealing computing resources. Once a botnet is active, the herder can use it for many tasks. They can perform distributed denial-of-service (DDoS) attacks. They can also steal data, send spam, or access the device's connection. Some criminals even rent these botnets out as commodities. They might offer "booter" or "stresser" services for profit.

Botnet architecture has evolved to avoid detection and disruption. The traditional method is the client–server model. In this setup, bots act as clients that communicate via existing servers. The bot herder sends commands to a central server. The server then relays those commands to all the infected clients. Some botnets use Internet Relay Chat (IRC) for this purpose. The herder creates an IRC channel and sets a topic. For example, a topic message could instruct the bots to begin a DDoS attack on a specific website. The bots then report their results back to the herder through the channel.

Stachledraht DDos Attack
Stachledraht DDos Attack

To make botnets more resilient, many now use peer-to-peer (P2P) networks. In a P2P botnet, there is no single central server to act as a point of failure. Instead, the bots act as both a client and a command distribution server. They communicate directly with one another. To find other infected machines, a P2P bot will discreetly probe random IP addresses. If it identifies another infected machine, it exchanges information. This information includes software versions and lists of known bots. If one bot has an older version, they initiate a file transfer to update. This allows the botnet to grow and update itself automatically.

P2P-network
P2P-network

Other methods of command and control include using web domains. Large botnets, such as the Rustock or Srizbi botnets, often use this approach. These bots access specially designed webpages to receive their commands. This method allows for easy updates with simple code. However, domains can be seized by government agencies. To prevent this, some use "fast-flux DNS." This technique allows control servers to change frequently. Some even use domain generation algorithms to create new names for controller servers. Others use free DNS hosting services to point subdomains toward their control centers.

Operating or building a botnet without authorization is illegal in most jurisdictions. It is regularly prosecuted as hacking, fraud, or other cyber-crimes. Law enforcement and private parties use legal tools to disrupt these networks. However, these takedowns can raise complex legal and constitutional issues. Modern botnets are increasingly sophisticated. Some even use popular sites like GitHub, Twitter, or Reddit to hide their communications. They may also use the Tor hidden services to avoid detection. Understanding these complex systems is vital for maintaining digital security in a connected world.

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CIAJMK1209-en.svg
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