What is Defense in depth (computing)?
{{for|the military strategy|Defence in depth}} [[File:Defense In Depth - Onion Model.svg|thumb|right|200px|{{Center|A graphical representation of the onion model of Defense in Depth, a concept in Information Security.}}]] '''Defense in Depth''' (also known as '''layered security''' and '''layered defense''') is an information assurance (IA) concept.<ref name=TR>{{cite web |url=http://www.techrepublic.com/blog/it-security/understanding-layered-security-and-defense-in-depth/ |title=Understanding layered security and defense in depth |publisher=TechRepublic |access-date=13 November 2015 |archive-date=15 November 2015 |archive-url=https://web.archive.org/web/20151115224132/http://www.techrepublic.com/blog/it-security/understanding-layered-security-and-defense-in-depth/ |url-status=dead }}</ref> It uses multiple layers of [[security]] controls (defenses) placed throughout an [[information technology]] (IT) system.<ref name=TR/> The multiple layers are not of the same security tool. It uses several different kinds of security with each protecting against a different security [[attack]].<ref name=TR/> ==Background== Defense in depth is originally a military [[strategy]]. It seeks to delay rather than prevent the advance of an attacker by yielding space to buy time.<ref>Michiko Phifer, ''A Handbook of Military Strategy and Tactics'' (New Delhi: Vij Books India Private Limited, 2012), p. 102</ref> The [[National Security Agency]] (NSA) changed the concept to be a [[Wikt:comprehensive|comprehensive]] approach to information and electronic security.<ref name=nsa1>{{Cite web |url=http://www.nsa.gov/ia/_files/support/defenseindepth.pdf |title=Defense in Depth: A practical strategy for achieving Information Assurance in today’s highly networked environments. |access-date=2015-11-13 |archive-date=2010-05-13 |archive-url=https://web.archive.org/web/20100513033807/http://www.nsa.gov/ia/_files/support/defenseindepth.pdf |url-status=dead }}</ref> The placement of protection mechanisms, procedures and policies is intended to incr