When smart hardware first entered millions of homes and offices, few imagined a digital weapon built entirely from security cameras, baby monitors, and home routers. In late 2016, that threat became reality when a massive malware strain knocked essential internet services offline across North America and Europe. That coordinated malware engine was the Mirai botnet.
Even years after its original authors were identified, the core code of the Mirai botnet remains one of the most widely copied frameworks in computer networking. By turning everyday consumer hardware into a synchronized army of bots, it permanently changed how engineers view connected device security.
To understand why this malware became so dominant, we must examine how it was programmed, how it runs in hardware memory, and how it launches multi-terabit traffic floods.
Table of Contents
What Is the Mirai Botnet and Why Is It Unique?
The Mirai botnet is a specialized network of infected smart devices controlled remotely by a central operator to launch distributed denial-of-service (DDoS) attacks.
[ Central Attacker ]
│
▼ (Sends Attack Command)
[ C2 Server (Go) ]
├───► [ Hijacked Camera (Bot 1) ] ───┐
├───► [ Hijacked Router (Bot 2) ] ───┼───► (Multi-Terabit SYN/UDP Flood) ───► [ Target Website / DNS ]
└───► [ Hijacked DVR (Bot 3) ] ───┘
What makes the Mirai botnet unique in computer engineering is its target audience. Traditional botnets infected desktop computers running Windows through phishing emails or infected web downloads.
The creators of the Mirai botnet realized that desktop PCs had active antivirus tools and local firewalls. Smart gadgets, on the other hand, run stripped-down embedded Linux systems on low-power microchips (such as ARM, MIPS, and x86 architectures). These devices stay online day and night, rarely have antivirus protection, and often retain their original factory passwords.
What Does the Mirai Botnet Architecture Look Like Under the Hood?
The software architecture of the Mirai botnet is divided into three primary components that run in coordination:
+-----------------------------------------------------------------------------------+
| Mirai Botnet Architecture |
+-----------------------------------------------------------------------------------+
| 1. Scanner Engine (Client) │ Fast asynchronous SYN probes over ports 23 and 2323 |
| 2. Loader / Delivery Server │ Downloads matching binary for MIPS, ARM, or x86 |
| 3. Command & Control (C2) │ Central Go-based server managing bot attack queues |
+-----------------------------------------------------------------------------------+
1. The Bot Client (Written in C)
The client program is written in standard C to keep it extremely fast and lightweight. It runs directly on the compromised hardware. Its job is to hide in memory, listen for attack instructions from the master server, and constantly scan the wider internet for new hardware to infect.
2. The Command and Control (C2) Server (Written in Go)
The central command console was built using Go (Golang). The operators log into this control interface to see how many active bots are registered and to issue synchronized attack commands.
3. The Payload Delivery Server (Loader)
Once a vulnerable gadget is found, the scanner notifies a dedicated loading server. This server connects to the target device via Telnet and uses simple shell commands like wget or tftp to install the exact binary compiled for that specific processor chip.
How Does the Mirai Botnet Scan and Infect Connected Devices?
The infection method of the Mirai botnet relies on automation and persistence. It follows four clear technical phases:
[ Phase 1: Port Probe ] ───► [ Phase 2: Brute-Force ] ───► [ Phase 3: Shell Setup ] ───► [ Phase 4: Process Kill ]
Scans Telnet 23/2323 Tries 68 default logins Downloads RAM payload Kills rival bots & closes port
1. Generating Random IP Targets
The bot client contains an asynchronous scanning module. It generates random IPv4 addresses and sends lightweight TCP SYN packets to ports 23 and 2323 (standard Telnet management ports). To avoid alerting network administrators, the source code contains hardcoded exclusions that prevent it from scanning IP ranges owned by the US Department of Defense, General Electric, and the US Postal Service.
2. Testing Hardcoded Default Credentials
When an open port responds, the Mirai botnet attempts to log in using a built-in table of 68 factory default username and password combinations. These include common defaults like:
root:xc3511admin:adminroot:vizxvsupport:support
Because these credentials match the factory settings of hundreds of white-label camera and router makers, the script succeeds on thousands of devices every hour.
3. Acquiring Shell Access and Running in Memory
Once authenticated, the scanner executes basic commands like /bin/busybox to verify that a functional Unix shell is available. It then downloads the malware binary and runs it directly in volatile RAM.
To hide from forensic investigations, the binary deletes its original file from the local file storage right after loading into memory. This means if an investigator looks at the disk storage, the file appears to be gone while the malicious process continues running in active RAM.
4. Eliminating Competitors and Closing the Door
To maintain exclusive control, the Mirai botnet acts aggressively against rival software:
- It scans active processes in
/procand terminates competing malware families (such as Qbot). - It binds to local TCP port 48101; if another instance is already running, it yields execution to prevent memory crashes.
- In many variants, it closes port 23 on the device so that other automated scanners cannot hijack the same hardware.
This operational sequence exposes how basic hardware neglect directly creates the widespread risks of IoT that attackers leverage across enterprise networks.
How Does the Mirai Botnet Launch Large-Scale DDoS Attacks?
When the central operator wants to take down an online platform, they send a single encrypted text string to the bot fleet. Every bot parses this message and immediately unleashes its network engine.
The Mirai botnet supports several distinct attack types to exhaust target resources:
| Attack Mode | Technical Mechanism | Network Impact |
| GRE Flood | Sends Generic Routing Encapsulation packets with random routing headers. | Chokes perimeter routers with packet decapsulation overhead. |
| SYN Flood | Sends endless TCP connection requests without completing the handshake. | Fills the target server connection memory table until it crashes. |
| ACK Flood | Floods servers with fake acknowledgment packets. | Forces firewalls to waste computing power tracking non-existent state tables. |
| UDP Plain Flood | Bombards target IP addresses with high-volume raw UDP packets. | Saturates total network bandwidth and transit pipes. |
| DNS Water Torture | Requests millions of random, fake subdomains (xyz123.target.com). | Exhausts authoritative DNS servers trying to look up non-existent records. |
Because tens of thousands of devices generate these packet floods simultaneously, the combined volume easily exceeds multiple terabits per second. Detailed investigations in Cloudflare technical analysis show that volumetric floods generated by these botnets can overwhelm even major content delivery networks.
These attack modes are part of the broader category of coordinated common IoT attacks that disrupt business services today.
What Happened During the Famous 2016 Dyn DNS Outage?
In October 2016, the real-world destructive potential of the Mirai botnet became clear to the general public.
Attackers directed a botnet consisting of an estimated 100,000 compromised security cameras, digital video recorders, and residential gateways against Dyn, a premier managed Domain Name System (DNS) company.
The attack flood approached 1.2 Terabits per second. Because Dyn handled domain name lookups for major internet platforms, internet users along the US East Coast suddenly lost access to GitHub, Twitter, Spotify, Netflix, Reddit, and Airbnb.
The incident proved a critical technological lesson: an insecure $30 security camera installed in a home living room could be weaponized to bring down enterprise cloud platforms thousands of miles away.
Why Does the Mirai Botnet Codebase Still Dominate in 2026?
Shortly after the original 2016 attacks, the creators publicly released the source code online. That release sparked an evolution that continues to shape network threats today.
Recent threat research shows that the Mirai botnet has evolved far beyond its original Telnet brute-forcing capabilities:
[ 2016 Original Mirai ] [ 2025-2026 Modern Variants ]
- Scans open Telnet (23/2323) - Exploits Zero-Day Web Flaws (CVEs)
- 68 Hardcoded Passwords - Persistent Systemd and Crontab Services
- Simple Centralized C2 - Multi-Tier C2 and P2P Protocols
- Cleared on Simple Reboot - Self-Replicating with FNV-1a Hashing
- Vulnerability-Driven Infection: Modern variants do not rely solely on default passwords. They scan for known remote code execution bugs (CVEs) in router web interfaces, network storage drives, and IP camera software.
- Permanent System Persistence: While the original version was cleared by a simple power reboot, modern variants modify system startup scripts (
/etc/rc.local),systemddaemon services, andcrontabscheduled jobs to reinstall themselves automatically after every reboot. - Advanced Strains: Offshoots like Mozi, Aisuru, and Nexcorium use encrypted peer-to-peer (P2P) control channels, making it nearly impossible to shut down the network by taking down a single central server.
How Can Hardware Makers and Network Engineers Defend Against Botnets?
Defending against the Mirai botnet family requires solving security flaws at both the hardware manufacturing stage and the network configuration stage:
+-------------------------------------------------------------+
| Anti-Botnet Technical Defenses |
+-------------------------------------------------------------+
1. Firmware Level │ Cryptographic Secure Boot & Signed Code
2. Access Level │ Permanent Ban on Default Factory Logins
3. Edge Level │ Global Block on Inbound Telnet (23) & UPnP
4. Network Level │ VLAN Segmentation & Outbound Rate Limiting
+-------------------------------------------------------------+
1. Enforce Hardware-Based Secure Boot
Device makers must implement cryptographic signature verification in device firmware. When a microchip boots, it should verify the digital signature of the kernel before execution. If malicious code has altered memory, the system should halt rather than run untrusted instructions. Companies designing commercial products should follow the engineering principles laid out in IoT development services to build secure boot pipelines from day one.
2. Eliminate Shared Factory Passwords
Modern regulations now require every device to ship with a unique, randomized password printed on its physical label, or force the user to set a strong password during initial setup. Technical specifications in NIST device cybersecurity standards explicitly require eliminating universal default credentials across all connected products.
3. Block Inbound Management Ports at the Perimeter
Network administrators should block inbound access to ports 23, 2323, and raw SSH from the public web. Routers must have Universal Plug and Play (UPnP) turned off to prevent local gadgets from punching holes through edge firewalls. Detailed operational guidance is available in official CISA exposure reduction guidance for minimizing internet-facing attack surfaces.
4. Implement Strong Interoperability and Isolation
Heterogeneous smart devices should never sit together on an open flat network. Applying verified network interoperability standards and placing connected hardware inside dedicated Virtual Local Area Networks (VLANs) stops infected units from scanning and pivoting to critical workstations. The foundational rules defined by the OWASP IoT security project provide a comprehensive framework for auditing these configurations.
Frequently Asked Questions
Can a simple device reboot remove the Mirai botnet?
Rebooting a device cleans the original Mirai malware because it runs entirely inside temporary RAM. However, if your router ports remain open and the factory password is unchanged, automated scanners will reinfect the hardware within two to five minutes after the reboot.
Which programming languages were used to build Mirai?
The Mirai client software was programmed in C to allow fast compilation across diverse CPU architectures. The Command and Control management server was programmed in Go (Golang) to handle concurrent network connections efficiently.
What kind of devices does Mirai infect most often?
Mirai primarily infects embedded Linux gadgets running on low-power processor architectures like ARC, MIPS, ARM, and x86. Common targets include digital video recorders, network cameras, home routers, and network-attached storage appliances.
Is the original Mirai botnet still active today?
The original 2016 botnet created by its first authors was dismantled after law enforcement intervention. However, its open-source code has spawned dozens of active variants that continue scanning the internet and launching attacks today.
The Lasting Impact on Network Technology
The Mirai botnet demonstrated that the biggest risk in modern computing is not always the complexity of software, but the neglect of basic hardware hygiene. By exploiting default credentials on resource-constrained chips, it built the largest volumetric attack network in history.
Securing the next generation of connected hardware requires moving away from open default configurations toward signed firmware, isolated subnets, and strict network perimeter controls.
