From Wikipedia, the free encyclopedia Billion laughs
Billion laughs
In computer security, a billion laughs attack is a type of ]>
denial-of-service (DoS) attack which is aimed at parsers &lol9;
of XML documents.[1] It’s also referred to as an XML
bomb or as an exponential entity expansion attack.[2] When an XML parser loads this document, it sees that it
The example attack consists of defining 10 entities, each includes one root element, “lolz”, that contains the text
defined as consisting of 10 of the previous entity, with “&lol9;”. However, “&lol9;” is a defined entity that ex-
the document consisting of a single instance of the pands to a string containing ten “&lol8;” strings. Each
largest entity - which expands to 1 billion copies of the “&lol8;” string is a defined entity that expands to ten
first entity. In the most frequently cited example, the “&lol7;” strings, and so forth. ?After all the entity expan-
first entity is the string "lol", hence the name "billion sions have been processed, this small ( http://msdn.microsoft.com/en-us/magazine/
[3] "CVE-2003-1564". Common Vulnerabilities and
2003-02-02.
Exposures. The MITRE Corporation.
http://cve.mitre.org/cgi-bin/
cvename.cgi?name=CVE-2003-1564. Retrieved
2011-06-01.
[4] Bryan Sullivan. "XML Denial of Service Attacks and
Defenses". http://msdn.microsoft.com/en-us/
magazine/ee335713.aspx. Retrieved 2011-12-21.
Retrieved from "http://en.wikipedia.org/w/index.php?title=Billion_laughs&oldid=467215981"
Categories:
• Denial-of-service attacks
• XML
• Computer security stubs
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