What is a Botnet? And How to Protect Your Business
- florencepritchatt
- Oct 30
- 7 min read
Updated: Nov 13
In Q1 of 2025 alone, the internet infrastructure company Cloudflare blocked 20.5 million DDoS attacks - a 358% year-on-year increase, and mitigated 22.2 tbps DDoS attacks in Q3. Many of those attacks are driven by botnets.
As businesses increasingly rely on connected devices, cloud services, APIs and distributed applications, the risk from botnet-driven campaigns is more real than ever. If you are responsible for business operations, marketing, customer trust or security strategy, understanding botnets is essential.
In this article we’ll explain:
What a botnet is
Why they exist
The types you should be aware of
How they work
What they do to your devices
Signs your business might be under attack
How your business can protect itself with external attack surface management such as GARi from RMI Cyber
Learn more to stay ahead of emerging threats and keep your business protected.
What is a botnet?
A botnet is a network of internet-connected devices such as computers, servers, IoT systems, or mobile phones, that have been infected with malware and taken over by a threat actor. Once compromised, these devices, often called bots or zombies, receive instructions from a command-and-control (C2) server or via peer-to-peer communication.
Botnets allow cyber criminals to launch large-scale cyber attacks such as DDoS, data theft, or spam campaigns. In today’s world of hybrid work and interconnected systems, botnets are a major part of the modern cyber threat intelligence landscape. Businesses and employees that fail to detect infected endpoints risk not only operational downtime but also reputational damage and regulatory breaches.
Why are botnets created?
Botnets are built for many purposes, such as financial, strategic, or disruptive. Some of the main reasons threat actors create botnets include:
DDoS Attacks: Overwhelming targets with traffic to disrupt business continuity.
Click Fraud: Generating fake clicks or impressions for profit.
Data Theft: Harvesting credentials, personal data, or intellectual property.
Malware Distribution: Delivering ransomware or spyware to new targets.
Botnet-as-a-Service: Selling access to other criminals.
Spam Campaigns: Distributing phishing emails and malware at scale.
Cryptomining: Using hijacked devices to help mine cryptocurrency
Espionage: Supporting state-sponsored or corporate surveillance operations.
These motives demonstrate why cyber security firms are increasingly turning to threat intelligence software and network intrusion detection systems to uncover early signs of botnet activity.
What are the different types of botnets?
Centralised Botnets
A centralised botnet uses one or more command-and-control (C2) servers to manage all infected devices. The simplicity makes them efficient, but easier to take down if C2 servers are discovered.
Decentralised (Peer-to-Peer) Botnets
These botnets rely on peer-to-peer communication, where each infected device can transmit commands. This makes them resilient and harder to dismantle, which is a growing concern in cyber threat intelligence monitoring.
Hybrid Botnets
A hybrid approach combines centralised control with peer-to-peer redundancy. This allows the botnet to stay active even if one system is disrupted, demonstrating why modern Attack Surface Management solutions must consider both architectures.
Mobile Botnets
Targeting smartphones and tablets, especially Android devices, these botnets exploit malicious apps or unsecured networks to perform attacks such as SMS fraud or credential theft.
IoT Botnets
IoT (Internet of Things) botnets use connected devices (cameras, routers, sensors, even smart hoovers, washing machines, lightbulbs and other WiFi enabled appliances!) that often lack strong security controls. In 2025, IoT botnets are one of the fastest-growing threats, linked to large-scale cyber attacks due to billions of devices with weak defences.
What are botnets used for? (And why they’re a growing threat)
Botnets are not harmless background noise on the internet, they are the engine rooms of today’s most destructive cyber attacks. Once activated, they can be weaponised at scale, turning thousands (sometimes millions) of ordinary devices into a coordinated digital army.
Here’s how threat actors use them and why your business should be concerned:
DDoS attacks: overwhelming systems until they collapse
A botnet can unleash millions of requests per second against your website or critical systems, overwhelming bandwidth, crashing customer portals, or halting e-commerce transactions. Even a few minutes of downtime can result in six-figure revenue losses and long-term reputational damage.
Spam and phishing campaigns: exploiting human trust
Infected machines are hijacked to send out vast quantities of phishing emails, often disguised as trusted brands. These emails trick employees or customers into revealing passwords, payment details, or downloading malware. One careless click can compromise an entire organisation.
Data theft and espionage: stealing your most valuable assets
Once inside your environment, bots can silently harvest sensitive data. This includes login credentials and intellectual property to customer records and supplier information. That data can be sold, ransomed, or used to infiltrate other organisations within your supply chain.
Cryptomining: draining your power and performance
Even if attackers aren’t seeking immediate disruption, your infrastructure can still be exploited for profit. Botnets often install hidden cryptominers that hijack your CPU and electricity, degrading performance, inflating costs, and shortening hardware lifespan.
Click fraud and digital manipulation: corrupting your marketing data
For marketing and e-commerce businesses, botnets can simulate human clicks, distort campaign analytics, and drain advertising budgets. Beyond wasted spend, the manipulation of marketing data can mislead business decisions and erode trust in your analytics.
Malware distribution: spreading ransomware and trojans
Botnets frequently serve as delivery networks for ransomware, spyware, and Trojans. Once one endpoint is infected, the malware spreads rapidly, encrypting data, exfiltrating files, or establishing hidden backdoors for future exploitation.
How do botnets work?
A botnet doesn’t appear overnight, it’s a step-by-step process that turns everyday devices into a weaponised network. Understanding this flow is key to stopping attacks before they take hold.
1. Infection
It begins with a compromise. Hackers spread malware through social engineering techniques, malicious downloads, fake software updates, or unsecured IoT devices. Once the code lands on a system, it installs silently and starts communicating with the attacker’s network.
2. Command and control connection
Each infected device (now called a “bot”) connects to a command-and-control (C2) network, either via central servers or peer-to-peer channels. This link allows threat actors to send instructions and update the malware remotely.
Modern botnets hide these communications using encryption and rapidly changing domains, making them extremely hard to detect without a network intrusion detection system such as GARi.
3. Command execution
When activated, all infected devices act as one. The attacker can order them to launch DDoS attacks, steal data, send spam, or install ransomware. Because these commands come from thousands of global IPs, the attack looks like legitimate traffic, overwhelming even well-protected networks.
4. Self-propagation
Many botnets are self-spreading. They scan the internet for other vulnerable systems, infect them automatically, and expand exponentially. This is how a single overlooked laptop or camera can quickly pull an entire business network into a botnet. Having attack surface management solutions in place helps close these open doors before they’re exploited.
5. Stealth and persistence
Botnets are designed to stay hidden. They disguise their processes, use encryption, and can reinstall themselves even after partial removal. Some operate quietly for months before striking, gathering credentials or sensitive data unnoticed.
What do botnets do to devices when they’re under its control?
When a device becomes part of a botnet, it may:
Slow down due to hidden background processes
Leak sensitive business or customer data
Consume excessive bandwidth or CPU resources
Act as a launchpad for attacks on other networks
Become blacklisted for sending spam or malware
Ultimately, a single infected endpoint can compromise your organisation’s entire infrastructure, especially if your external attack surface management strategy is weak.
How do hackers control a botnet?
Once a device is infected, hackers need a way to manage and coordinate all the compromised machines. This is done through two main control structures - centralised and decentralised - each with its own risks and challenges for defenders.
Centralised control
In a centralised botnet, every infected device connects to a single command-and-control (C2) server that sends out instructions. This makes it easy for hackers to launch attacks quickly, like DDoS campaigns or data theft.
However, it’s also a weakness, as if the main C2 server is detected and blocked, the entire botnet can be shut down. Security tools such as threat intelligence software and network intrusion detection systems look for these communication links to stop attacks early.
Decentralised (peer-to-peer) control
Decentralised botnets have no single command point. Each infected device shares information with others, spreading commands across the network. This makes the botnet far harder to disable, forcing cyber security firms to focus on behaviour-based detection rather than tracing one server.
What are the different types of botnet attacks?
Network Flooding (DDoS): Overwhelms bandwidth and takes services offline.
Credential Stuffing: Automates login attempts to compromise accounts.
Spam Distribution: Uses your IPs to spread phishing or malware.
Cryptojacking: Drains resources for cryptocurrency mining.
Data Exfiltration: Extracts sensitive information from compromised systems.
Ad Fraud: Generates fake traffic or clicks to manipulate ad metrics.
These are no longer isolated events, they’re components of broader, coordinated cyber attacks often linked to threat actors.
Signs your devices may be in a botnet
Slower network performance or unexplained bandwidth spikes
Unauthorised outbound connections or API calls
Systems rebooting unexpectedly
Security alerts from your network intrusion detection system
Reports that your domain or IP is blacklisted for spam
High CPU usage or system overheating
If you notice these signs, act quickly, isolate the affected device, disconnect it from the network, and investigate using cyber threat intelligence data and attack surface management solutions like GARi.
But the reality is, by the time you see these symptoms, the damage may already be done. Botnets are designed to operate silently for weeks or months before triggering visible issues. That’s why ongoing, automated monitoring is far more effective than reacting after an attack or suspicious activity.
Botnets FAQ
Can a botnet infect cloud environments?
Yes. As more workloads move to the cloud, compromised credentials or misconfigured APIs can allow botnets to spread through virtual machines and containers, making external attack surface management crucial.
Are mobile devices at risk?
Yes. Mobile botnets exploit malicious apps and unsecured Wi-Fi to steal data or send spam. Regular updates and mobile endpoint protection are essential.
How do network intrusion detection systems help?
They analyse traffic in real time, flagging patterns associated with C2 communications or unusual outbound traffic, helping businesses identify botnet infections early.
Why is cyber risk compliance important for botnet defence?
Compliance enforces good security hygiene. Patching, access control, encryption, monitoring reduce the vulnerabilities botnets exploit.
How can threat intelligence improve botnet protection?
By providing early warning of emerging botnet activity, threat intelligence software helps your teams prioritise threats and update defences before attacks escalate.
Secure your business with GARi from RMI Cyber
GARi unifies threat intelligence, attack surface management, and network intrusion detection in one platform. It gives you full visibility across your digital ecosystem, enabling faster detection of infected endpoints and botnet activity.
Proactive, data-driven, and automated - GARi helps you stay compliant, reduce attack exposure, and defend your business before threats escalate.
Book a demo today and discover how GARi can secure your organisation against botnets and beyond.
