Definition of Conficker

Conficker, also known as Downup or Kido, is a computer worm that targets Microsoft Windows operating systems. Discovered in 2008, it primarily spreads through network connections and infected removable devices such as USB drives. The worm is designed to gain unauthorized access to and control of computer systems, potentially allowing hackers to steal personal information, install malicious software, or create botnets.


The phonetic pronunciation for the word “Conficker” would be: [kuh n-FIHK-er]

Key Takeaways

  1. Conficker is a notorious computer worm that targets the Microsoft Windows operating system, exploiting a vulnerability in the software to gain control over computers and networks.
  2. The worm is known for its ability to spread rapidly, create large botnets, and deploy various forms of malware, including ransomware and spyware, to compromise user data and security.
  3. To protect against Conficker, it is crucial to keep systems updated with security patches, maintain strong passwords, and employ reliable antivirus software that can detect and remove the worm.

Importance of Conficker

Conficker, also known as Downup or Downadup, is a significant term in technology because it is one of the most prolific and notorious computer worms in history.

Identified in 2008, Conficker exploits a vulnerability in Microsoft Windows operating systems to spread to other computers across networks, including shared resources and removable media.

Once infected, a compromised system links to a botnet, where cybercriminals can collect personal information, install malicious software, and perpetrate cyberattacks.

Despite vast efforts to counteract it, Conficker remains a significant security threat, illustrating the importance of regularly updating software, practicing cybersecurity hygiene, and raising awareness about online threats.


Conficker, also known as Downup, Downadup, or Kido, is a malicious computer worm that gained notoriety in late 2008 and continued to wreak havoc well into 2009. Its primary purpose was to take control of vulnerable computer systems, spread rapidly across networks, and exploit security vulnerabilities in the Microsoft Windows operating system. Once it had infiltrated a system, Conficker would create a botnet – a network of infected devices that could be remotely controlled by its creators, called “botmasters.” Botnets are typically used for a variety of illicit purposes, such as launching massive Distributed Denial of Service (DDoS) attacks, disseminating spam emails, and stealing sensitive information like login credentials and banking data.

In the case of Conficker, the worm was employed to deploy rogue security software and help its creators generate revenue through online advertisement scams and other fraudulent activities. To accomplish its objectives, Conficker employed several sophisticated mechanisms that enabled it to avoid detection, disable cybersecurity measures, and ensure its propagation. For instance, the worm utilized a domain generation algorithm (DGA) to communicate with its command and control servers, making it difficult for security researchers to pinpoint and disrupt its operations.

This advanced feature, combined with its ability to disable Windows security updates and Windows Defender, allowed Conficker to persistently maintain its presence on infected machines. Moreover, it would propagate through various means, such as exploiting a vulnerability in Windows Server service, spreading via infected removable media like USB drives, and brute-forcing weak administrator passwords on networked devices. At its peak, Conficker had infiltrated millions of computers worldwide, prompting an international effort among public and private entities to contain and mitigate the threat posed by this notorious computer worm.

Examples of Conficker

Conficker, also known as Downup, Downadup, or Kido, is a computer worm that targets the Microsoft Windows operating system. It was first detected in November 2008 and became one of the most notorious malware infections in history. Here are three real-world examples of Conficker’s impact:

Ukraine and the Hryvnia (UAH) Exchange Rate:In January 2009, the Central Bank of Ukraine was infected by the Conficker worm. The worm spread rapidly across the bank’s internal network, causing major disruptions. The infection impacted financial transactions and led to periodic freezes of the exchange rate for the Ukrainian Hryvnia (UAH), which only exacerbated the country’s ongoing economic crisis at that time.

United Kingdom National Health Service (NHS) Infection:In February 2009, Conficker infected computers at NHS hospitals across England and Scotland. The worm blocked access to medical records, causing delays in patient treatment and affecting hospital administration. More than 4,000 computers were infected across 15 hospitals in the Sheffield area alone, forcing the hospitals to rely on manual procedures.

French Navy Intranet Breach:In January 2009, the French Navy suffered a significant computer network intrusion due to Conficker. The worm infected around 800 computers within the navy’s intranet, forcing the shutdown of several systems, including those used for email communication and aircraft maintenance. The infection spread rapidly, causing downtime on essential communication systems and delaying operations.These examples showcase the various ways Conficker impacted different sectors and industries, highlighting the need for effective cybersecurity measures to protect against such threats.

FAQ – Conficker

What is Conficker?

Conficker, also known as Downup, Downadup, and Kido, is a computer worm that targets the Microsoft Windows operating system. It was first detected in November 2008 and has since infected millions of computers worldwide. Conficker spreads through various methods, including exploiting weaknesses in Windows OS, removable media (such as USB drives), and network shares.

How does Conficker infect a system?

Conficker infects a system by exploiting a vulnerability in Windows Server service, which allows the worm to execute code remotely. Once inside the system, the worm creates copies of itself, disables certain security features, and connects to a command and control server to receive further instructions. It can spread through network shares by guessing or brute-forcing administrator passwords and can also propagate using removable media like USB drives.

What are the signs of a Conficker infection?

Some possible signs of a Conficker infection include slow system performance, increased network traffic, disabled security services, inability to access certain websites (e.g., antivirus or security-related websites), and the presence of unfamiliar files or processes on your computer.

How can I remove Conficker from my computer?

To remove Conficker from your computer, it’s essential to first disconnect the infected computer from the network to prevent the worm from spreading further. Next, use a reputable antivirus or malware removal tool, such as Microsoft’s Malicious Software Removal Tool, to scan and remove the Conficker worm. After the removal, update your Windows operating system, and enable all security settings and services that were disabled by the worm to secure your computer.

How can I prevent a Conficker infection?

To prevent a Conficker infection, keep your Windows operating system and all software updated with the latest security patches. Install and regularly update a reputable antivirus program, enable Windows Firewall, and use strong passwords for your administrator accounts. Additionally, be cautious when using removable media (e.g., USB drives) and connecting to shared networks, as this can be a method of spreading the worm.

Related Technology Terms


  • Computer Worm
  • Microsoft Windows
  • Botnet
  • Remote Code Execution
  • Zero-Day Vulnerability


Sources for More Information


About The Authors

The DevX Technology Glossary is reviewed by technology experts and writers from our community. Terms and definitions continue to go under updates to stay relevant and up-to-date. These experts help us maintain the almost 10,000+ technology terms on DevX. Our reviewers have a strong technical background in software development, engineering, and startup businesses. They are experts with real-world experience working in the tech industry and academia.

See our full expert review panel.

These experts include:


About Our Editorial Process

At DevX, we’re dedicated to tech entrepreneurship. Our team closely follows industry shifts, new products, AI breakthroughs, technology trends, and funding announcements. Articles undergo thorough editing to ensure accuracy and clarity, reflecting DevX’s style and supporting entrepreneurs in the tech sphere.

See our full editorial policy.

More Technology Terms

Technology Glossary

Table of Contents