Network Working Group R. Fielding Request for Comments: 2616 ...

they would protect any system that contains or transports sensitiveinformation. In particular, log information gathered at proxies oftencontains highly sensitive personal information, and/or informationabout organizations. Log information should be carefully guarded, andappropriate guidelines for use developed and followed. (Section15.1.1).Fielding, et al. Standards Track [Page 155]RFC 2616 HTTP/1.1 June 1999Caching proxies provide additional potential vulnerabilities, sincethe contents of the cache represent an attractive target formalicious exploitation. Because cache contents persist after an HTTPrequest is complete, an attack on the cache can reveal informationlong after a user believes that the information has been removed fromthe network. Therefore, cache contents should be protected assensitive information.Proxy implementors should consider the privacy and securityimplications of their design and coding decisions, and of theconfiguration options they provide to proxy operators (especially thedefault configuration).Users of a proxy need to be aware that they are no trustworthier thanthe people who run the proxy; HTTP itself cannot solve this problem.The judicious use of cryptography, when appropriate, may suffice toprotect against a broad range of security and privacy attacks. Suchcryptography is beyond the scope of the HTTP/1.1 specification.15.7.1 Denial of Service Attacks on ProxiesThey exist. They are hard to defend against. Research continues.Beware.16 AcknowledgmentsThis specification makes heavy use of the augmented BNF and genericconstructs defined by David H. Crocker for RFC 822 [9]. Similarly, itreuses many of the definitions provided by Nathaniel Borenstein andNed Freed for MIME [7]. We hope that their inclusion in thisspecification will help reduce past confusion over the relationshipbetween HTTP and Internet mail message formats.