What is a Botnet?

Botnet Attack

April 07, 2025

Imagine waking up to find your smart refrigerator sending spam, your webcam participating in a massive attack on a government website, and your laptop secretly mining cryptocurrency for someone halfway across the world. This nightmare scenario is the reality of a botnet infection. Your devices—silently enslaved—join thousands or even millions of others in an invisible zombie army, carrying out their master's bidding while you remain completely unaware.

In October 2016, an unprecedented cyberattack brought down major websites like Twitter, Netflix, and CNN for hours. The culprit? A massive botnet called Mirai that had infected over 600,000 devices—most of them ordinary webcams, DVRs, and home routers. The attack demonstrated how everyday objects in our homes could be weaponized without our knowledge. This is the unsettling power of botnets: networks of compromised devices that operate under hidden control, transforming our personal technology into pawns in cybercriminal operations.

Inside the Digital Army: How Botnets Are Built and Controlled

Think of a botnet as a shadow army with a military-like command structure. At the top sits the "botmaster"—the criminal mastermind who orchestrates the network's activities. Just as military leaders don't speak directly to every soldier, botmasters create sophisticated control systems to manage their digital legions, which can number in the millions.

Modern botnets employ three primary architectural strategies, each with distinct advantages for cybercriminals:

• Centralized architecture: Like a traditional military with direct chain of command—infected devices connect directly to command servers. This structure offers simple control but creates an Achilles' heel; if authorities locate and shut down the central servers, the entire botnet collapses.
• Decentralized (P2P) architecture: Imagine a guerrilla force without a central base—each infected device communicates with others nearby, passing commands throughout the network. This structure makes takedown attempts nearly impossible since there's no central point to target.
• Hybrid architecture: The most sophisticated approach combines both strategies, using lieutenant-like proxy servers that shield the main command center while maintaining efficient control.

The Gameover Zeus botnet, which stole over $100 million from banks worldwide before its disruption in 2014, exemplified the evolution of these architectures. It began with a centralized structure but quickly adopted a P2P approach after early disruption attempts, allowing it to survive for years despite massive international efforts to destroy it.

The largest modern botnets don't just target computers. The 2023 Meris botnet primarily infected IoT devices and network equipment, demonstrating how our expanding digital ecosystem creates new vulnerabilities. With an estimated 15+ million compromised devices, it became one of history's largest digital armies, capable of launching attacks exceeding 20 Tbps—enough to temporarily cripple even the most robust internet infrastructure.

The Digital Underground Economy: Why Criminals Build Botnets

In September 2023, a mid-sized manufacturing company suddenly found their website offline during a critical product launch. The culprit wasn't a competitor—it was a 16-year-old who had rented DDoS services for $50 from a botnet operator on the dark web. This incident illustrates how botnets have transformed from specialized hacking tools into accessible, commoditized services in the cybercriminal underground.

Today's botnets function much like illegal businesses with diversified revenue streams. The most profitable operations can generate millions in annual revenue through various monetization channels:

What makes botnets particularly lucrative is that operators have developed a criminal franchise model. Rather than limiting themselves to a single revenue stream, they rent botnet capabilities to other criminals through specialized marketplaces:

• "DDoS-for-hire" services allow anyone to launch massive attacks starting at just $10/hour or $200/day
• Access brokers sell initial entry to valuable corporate networks for $500-$10,000 depending on the target's size and industry
• Traffic distribution services redirect victim browsers to advertising fraud schemes, earning $3-$5 per 1,000 redirects
• Proxy services rent compromised devices as anonymous relays, charging $1-$5 per device monthly

A single sophisticated botnet can operate across all these business models simultaneously, with specialized teams handling different aspects of operations. The Emotet botnet, for example, evolved from a simple banking trojan into what security researchers called "malware-as-a-service infrastructure," providing initial access to other threat actors who would deploy ransomware that extorted millions from victims.

DDoS & Botnet Attacks in 2025:

• GorillaBot: Advanced Mirai Variant Targeting IoT Devices with Enhanced DDoS Capabilities
• New FritzFrog Botnet Sample Exploits Log4Shell and PwnKit
• NoaBot Botnet: The Latest Mirai Offspring
• InfectedSlurs Botnet Exploits Zero-Days to Spread Mirai Malware
• DarkGate and Pikabot Copy the QakBot Malware
• IPStorm Botnet Stopped by the FBI, Operator Detained
• IoT Malware Attacks Grow by 400% in 2023
• Mirai variant "Pandora" infects Android TV for DDoS attacks.

When Digital Armies Attack: The Real-World Impact of Botnets

On a frigid morning in 2015, residents across western Ukraine found themselves suddenly plunged into darkness. The power outage—affecting nearly 230,000 people during winter—wasn't caused by a storm or equipment failure. It was the work of hackers using the BlackEnergy botnet to deliberately shut down critical infrastructure. This unprecedented attack demonstrated how botnets could reach beyond the digital realm to impact physical safety and human lives.

The real-world consequences of botnet attacks continue to grow in severity:

• Healthcare disruption: In 2020, during the COVID-19 pandemic, botnet attacks targeted hospitals and healthcare providers, forcing some facilities to divert emergency patients and delay critical procedures. In at least one documented case, a German patient died after being redirected to a more distant hospital during a ransomware attack facilitated by botnet access.
• Financial losses: Banking botnets like Zeus, Trickbot, and QBot have collectively stolen billions from financial institutions and their customers. The FBI estimates that a single Zeus botnet variant caused over $100 million in losses to US banks alone.
• Service disruptions: The 2016 Mirai attack against DNS provider Dyn demonstrated how botnet attacks could cause cascading failures across the internet, temporarily rendering major platforms like Twitter, Reddit, and Netflix inaccessible across much of North America and Europe.
• Privacy violations: In 2021, security researchers uncovered a botnet specifically targeting home security cameras, exfiltrating private footage from thousands of homes. The footage later appeared for sale on dark web marketplaces.
• Infrastructure targeting: Modern botnets increasingly target critical infrastructure, with documented attempts against water treatment facilities, power grids, and transportation systems. A successful attack could potentially cause widespread physical harm.

Perhaps most concerning is how botnets amplify geopolitical tensions. Nation-state actors increasingly deploy them for both espionage and disruptive attacks. In 2022, the Russia-linked Cyclops Blink botnet specifically targeted network devices in NATO countries, creating persistent access that could be leveraged during international conflicts. The line between cybercrime and cyberwarfare continues to blur, with civilian devices unwittingly drafted into digital conflicts.

Signs Your Devices Have Been Drafted: Detecting Botnet Infections

When Sarah noticed her laptop battery draining unusually quickly and her internet speeds slowing to a crawl, she assumed her three-year-old computer was simply showing its age. It wasn't until her bank called about suspicious transfers that she discovered the truth: her laptop had been part of a banking botnet for months, silently monitoring her financial activities while using her resources for other attacks.

Unlike ransomware that announces its presence with encryption and ransom notes, botnet malware works tirelessly to remain invisible. Modern variants implement sophisticated evasion techniques that can fool even experienced users. However, watching for these telltale signs can help you identify a potential infection:

Observable System Indicators

• Your computer fans run loudly even when you're not using resource-intensive applications—a possible sign of hidden cryptocurrency mining
• Battery life suddenly decreases dramatically on laptops or mobile devices
• Unexplained spikes in internet data usage, particularly during periods when you're not actively using the device
• The mouse cursor moves on its own, applications launch without your action, or you see browser windows opening spontaneously
• Security software suddenly stops working or cannot be updated
• Strange console windows flash briefly on screen before disappearing
• Your search engine results are redirected, or unexpected toolbars and extensions appear in your browser
• Family, friends, or colleagues receive suspicious messages from your accounts that you didn't send
• Your online accounts show login attempts from unfamiliar locations

Technical Detection Methods

• Network traffic analysis: Using tools like Wireshark to identify unusual connection patterns, particularly to IP addresses or domains with known bad reputations
• Process inspection: Examining Task Manager or Process Explorer for suspicious processes with random names or unusual parent-child relationships
• DNS request monitoring: Looking for domain generation algorithm (DGA) patterns—computer-generated domains like "xjdhshe.com" or "nsjeichs83.net"
• Port scanning: Running tools like netstat to identify unexpected open ports that could indicate backdoor access
• Memory analysis: Using specialized forensic tools to detect fileless malware that exists only in RAM

In one remarkable case, security researchers identified a botnet infection when they noticed a computer was sending small data packets exactly every 10 minutes, 24 hours a day—a precision that human users simply don't exhibit. This regular "heartbeat" communication revealed the presence of a command and control connection.

If you observe multiple indicators, your system may be compromised and requires immediate remediation. While botnet operators typically focus on network-level operations rather than targeting individual users' data, the presence of botnet malware creates significant security risks that should not be ignored. For more information about detecting hidden network connections, see this guide on identifying covert communication channels.

Building Your Digital Fortress: Protecting Against Botnet Infections

When James, an IT manager at a manufacturing firm, discovered that company servers were participating in a DDoS attack against a competitor, the investigation revealed a shocking truth: the initial compromise had occurred 14 months earlier through an unpatched vulnerability. The attackers had maintained silent access all that time, waiting for the perfect moment to monetize their access.

This scenario highlights why prevention is crucial—once established, botnet infections can persist for months or years before detection. Modern botnet malware employs multiple infection vectors and persistence techniques that require a multi-layered defense strategy:

System Hardening: Your First Line of Defense

• Keep all software updated: The Wannacry ransomware that infected over 230,000 systems relied on a vulnerability that had been patched months earlier. Automatic updates for your operating system and applications close security holes before they can be exploited.
• Implement proper network segmentation: When the Target retail breach occurred, attackers initially accessed an HVAC vendor's systems but easily moved to payment systems due to poor network segregation. Using VLANs and separate networks for IoT devices can contain potential compromises.
• Secure IoT devices: The Mirai botnet primarily infected devices with factory-default passwords. Change these immediately, disable unnecessary services, and consider a dedicated IoT network isolated from your main systems.
• Enable multi-factor authentication: When the 2020 SolarWinds supply chain attack compromised thousands of organizations, those with strict MFA requirements significantly limited the attackers' ability to move laterally within their networks.
• Apply the principle of least privilege: Most botnet malware requires administrative access to fully establish persistence. Running with standard user privileges and employing User Account Control (UAC) creates additional barriers to infection.

Security Tools: Your Active Defense System

• Deploy reputable security software: Modern solutions with behavior-based detection can identify previously unknown threats based on suspicious activities rather than relying solely on known signatures.
• Implement DNS filtering: Services like Quad9 or NextDNS can block connections to known command and control servers, effectively cutting off infected devices from receiving instructions.
• Enable network monitoring: Tools like Glasswire can alert you to unusual outbound connections or data usage patterns that might indicate botnet communication.
• Use a hardware firewall: Unlike software firewalls that can be disabled by malware, hardware firewalls provide an additional layer of protection that's much harder to circumvent.
• Consider endpoint detection and response (EDR) solutions: These advanced tools continuously monitor for suspicious behaviors and can automatically isolate compromised systems before damage spreads.

Human Practices: Your Ongoing Security Culture

• Practice cautious browsing: The majority of infections begin with deceptive websites. Be particularly wary of sites promising free software, media, or deals that seem too good to be true.
• Be skeptical of email attachments: Before opening attachments or clicking links, verify the sender through another communication channel. Even messages that appear to come from known contacts can be spoofed.
• Use strong, unique passwords: Credential stuffing attacks rely on password reuse across services. Password managers make it easy to maintain different strong passwords for each service.
• Consider script blocking extensions: Browser extensions like NoScript or uBlock Origin can prevent malicious JavaScript from executing, blocking many exploit kits used to deliver botnet malware.

For comprehensive protection, specialized anti-malware solutions with behavioral detection, like GridinSoft Anti-Malware, can identify and block botnet installation attempts based on suspicious behavior patterns even when malware uses novel techniques to evade traditional signature-based detection. To learn more about protecting your home router from botnet infections, check out this comprehensive router security guide.

Breaking Free: Reclaiming Your Devices from Botnet Control

When Mark's small accounting firm became collateral damage in a botnet attack targeting their client, the resulting business disruption cost them nearly $30,000 in recovery expenses and lost productivity. "The worst part was knowing our systems were being used to attack our own client," Mark explained. "It was like our digital identities had been hijacked."

Discovering a botnet infection requires swift, methodical remediation. Modern botnet malware implements sophisticated persistence mechanisms that can resist simple removal attempts. Follow this comprehensive incident response plan:

Immediate Containment: Stop the Bleeding

• Disconnect from networks: Immediately isolate the infected system from all networks (both wired and wireless) to prevent command and control communication and lateral movement. In corporate environments, consider physically unplugging network cables rather than relying on software disconnection.
• Disable remote access: Temporarily disable all remote access protocols and services which could be used as persistence channels.
• Document indicators: Before shutting down, capture screenshots of unusual processes, network connections, or other anomalies that might help identify the specific threat.

Thorough Remediation: Clean House

• Boot into safe mode: Starting Windows in safe mode prevents many malware components from loading automatically, making them easier to remove.
• Perform offline scanning: Using bootable media removes the possibility that active malware will interfere with the cleaning process. This approach is particularly effective against rootkits that hide within the operating system.
• Consider professional forensic analysis: For business environments or systems containing sensitive data, professional incident response may be necessary to determine if data exfiltration occurred.
• Verify persistence locations: Botnet malware typically establishes multiple persistence mechanisms. Check startup folders (shell:startup), scheduled tasks, registry auto-run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run), and service entries for suspicious items.
• Reset browser settings: Many botnets modify browser settings to maintain persistence or monitor activity. Clearing extensions, cached data, cookies, and resetting to default configuration eliminates these footholds.

Post-Remediation Security: Prevent Reinfection

• Change all credentials: Any passwords used on the compromised system should be considered exposed. Prioritize financial, email, and administrative accounts when updating credentials.
• Monitor for reinfection: After cleanup, monitor system behavior closely for signs of persistent access or reinfection attempts. Many sophisticated botnets will attempt to re-establish control.
• Patch vulnerabilities: Identify and address the initial infection vector. Was it an unpatched vulnerability, a phishing email, or compromised credentials? Closing this security gap prevents immediate reinfection.
• Implement stronger security controls: Use the incident as an opportunity to enhance your security posture with additional monitoring and prevention tools.
• Report the incident: For significant compromises, consider reporting to organizations like the FBI's Internet Crime Complaint Center (IC3) or your national CERT. These reports help track botnet activity and potentially lead to botnet takedowns.

For comprehensive remediation, GridinSoft Anti-Malware provides specialized tools designed to detect and remove persistent botnet components, including advanced features for restoring hijacked browser settings and removing deeply embedded persistence mechanisms. For additional guidance on handling advanced threats, see this expert guide on removing sophisticated malware like Cobalt Strike.

Case Study: Banking Botnet Infection

In a recent incident response case, a financial institution discovered Emotet botnet infections across multiple workstations. The initial compromise occurred through a phishing email with a malicious Office document that exploited a macro vulnerability. After installation, the botnet malware established persistence through scheduled tasks, registry modifications, and WMI event subscriptions.

The malware disabled security controls, began exfiltrating banking credentials, and ultimately served as a distribution platform for Ryuk ransomware. What started as a seemingly minor botnet infection escalated to a potential million-dollar ransomware incident. Complete remediation required offline scanning, credential resets, network traffic analysis, and implementation of enhanced email filtering and application whitelisting to prevent reinfection.

Frequently Asked Questions