Editing Code Red (computer worm) (section)

==Concept==

===Exploited vulnerability===
The worm showed a vulnerability in software distributed with IIS, described in Microsoft Security Bulletin MS01-033 (CVE-2001-0500),<ref>[https://web.archive.org/web/20060831221910/http://www.microsoft.com/technet/security/bulletin/MS01-033.mspx MS01-033 "Microsoft Security Bulletin MS01-033: Unchecked Buffer in Index Server ISAPI Extension Could Enable Web Server Compromise"], Microsoft Corporation, June 18, 2001</ref> for which a patch had become available a month earlier.

The worm spread itself using a common type of vulnerability known as a [[buffer overflow]]. It did this by using a long string of the repeated letter 'N' to overflow a buffer, allowing the worm to execute arbitrary code and infect the machine with the worm. Kenneth D. Eichman was the first to discover how to block it, and was invited to the [[White House]] for his discovery.<ref>{{cite web|url=http://news.cnet.com/2009-1001-270471.html|title=Virulent worm calls into doubt our ability to protect the Net|last=Lemos|first=Rob|work=Tracking Code Red|publisher=CNET News|url-status=live|archive-url=https://web.archive.org/web/20110617101100/http://news.cnet.com/2009-1001-270471.html|archive-date=June 17, 2011|access-date=March 14, 2011}}</ref>

===Worm payload ===
The payload of the worm included:

* [[Website defacement|Defacing]] the affected web site to display:

 HELLO! Welcome to <nowiki>http://www.worm.com</nowiki> ! Hacked By Chinese!

* Other activities based on the day of the month:<ref>{{cite web |title=CERT Advisory CA-2001-19: 'Code Red' Worm Exploiting Buffer Overflow In IIS Indexing Service DLL |url=http://www.cert.org/advisories/CA-2001-19.html |work=CERT/CC |date=July 17, 2001 |access-date=June 29, 2010}}</ref>
** Days 1-19: Trying to spread itself by looking for more IIS servers on the Internet.
** Days 20–27: Launch [[denial of service]] attacks on several fixed [[IP address]]es. The IP address of the [[White House]] web server was among these.<ref name="caida" />
** Days 28-end of month: Sleeps, no active attacks.

When scanning for vulnerable machines, the worm did not test whether the server running on a remote machine was running a vulnerable version of IIS, or even whether it was running IIS at all. [[Apache HTTP Server|Apache]] access logs from this time frequently had entries such as these:

{{pre|1=GET /default.ida?NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN%u9090%u6858%ucbd3%u7801%u9090%u6858%ucbd3%u7801%u9090%u6858%ucbd3%u7801%u9090%u9090%u8190%u00c3%u0003%u8b00%u531b%u53ff%u0078%u0000%u00=a  HTTP/1.0}}

The worm's payload is the string following the last 'N'. Due to a buffer overflow, a vulnerable host interpreted this string as computer instructions, propagating the worm.