Code Red Malware: Full Overview
Published: 1/20/2026
Written by: Lizzie Danielson
Learn what Code Red malware is, how it spreads, and how to detect and remove it before it impacts your systems.
What is Code Red malware?
The Code Red malware is a self-propagating worm designed to exploit software vulnerabilities, particularly targeting Microsoft IIS servers. Also referred to simply as "Code Red," it gained notoriety for its ability to spread rapidly and disrupt web services. Its primary purpose was website defacement, with a specific payload that displayed "Hacked by Chinese!" on affected websites, and initiating DoS attacks. The threat level of Code Red was considered high due to its rapid spread and system-wide impact.
When was Code Red first discovered?
Code Red was first discovered on July 13, 2001. The worm exploited a known buffer overflow vulnerability in Microsoft IIS (CVE-2001-0500). Its blistering speed affected over 359,000 hosts within hours of its initial identification.
Who created Code Red?
The identities and number of individuals behind Code Red remain unknown. While speculation arose regarding the message "Hacked by Chinese," no definitive evidence connected the worm to any specific actor or group.
What does Code Red target?
Code Red primarily targets servers running unpatched versions of Microsoft IIS. Industries heavily reliant on web infrastructure, such as government organizations, enterprises, and service providers, were notably impacted. Geographically, its reach extended globally due to the prevalence of IIS at the time.
Code Red distribution methods
Code Red propagated itself via the internet by scanning and targeting IP ranges that hosted vulnerable IIS servers. It exploited the buffer overflow vulnerability in HTTP requests, infiltrating systems and then scanning for additional vulnerable servers to replicate.
Technical analysis of Code Red malware
Code Red operated as a memory-resident worm, meaning it didn’t write files but instead used resources in memory. Its infection method involved sending specially crafted HTTP requests to trigger a buffer overflow in IIS servers. Once infected, the worm executed its payload, which varied depending on its version. Code Red is best known for web defacement, but it also launched distributed denial-of-service attacks against specific targets, such as whitehouse.gov.
Tactics, Techniques & Procedures (TTPs)
MITRE ATT&CK Techniques
T1190: Exploit Public-Facing Applications
T1095: Non-Application Layer Protocol (HTTP for payload delivery)
T1071: Application Layer Protocol (for communication)
Indicators of Compromise (IoCs)
Unusual HTTP traffic targeting port 80 with "GET" requests
Defacement messages on web pages, such as "Hacked by Chinese!"
Abnormal traffic spikes indicative of scanning activity
Malware Guide
Our malware guide shows you how to shut down those infiltration paths before they ever become a crisis.
How to know if you’re infected with Code Red?
Systems infected with Code Red exhibit several telltale signs, including unauthorized website defacement, unresponsive IIS servers, and significant spikes in HTTP traffic or scanning activity. Administrators may also notice performance degradation or unusual log entries related to exploit attempts.
Code Red removal instructions
Removing Code Red requires immediate disconnection from the network to prevent further spread. Administrators should update IIS servers with security patches like Microsoft’s MS01-033 immediately. Leveraging EDR tools like Huntress can detect and remediate residual memory-resident threats effectively.
Is Code Red still active?
While Code Red itself no longer poses a significant direct threat, its legacy serves as a reminder of how unpatched systems can be compromised. Variants and other worms mimicking its behavior occasionally emerge, highlighting the importance of ongoing vigilance.
Mitigation & prevention strategies
Preventing similar threats involves a combination of proactive measures:
Keep systems updated with the latest patches.
Implement robust firewall rules to monitor and block abnormal traffic.
Train users to recognize potential vulnerabilities, leveraging Huntress SAT.
Utilize managed detection and remediation services like Huntress for 24/7 monitoring and threat mitigation.
Related educational articles & videos
Code Red FAQs
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