Editing Denial-of-service attack (section)

{{Short description|Type of cyber-attack}}
{{Redirect|DoS|other uses|DOS (disambiguation)}}
{{Redirect|DDoS|the non-profit whistleblower site|Distributed Denial of Secrets}}
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{{Use dmy dates|date=May 2024}}

[[File:Stachledraht DDos Attack.svg|thumb|Diagram of a DDoS attack. Note how multiple computers are attacking a single computer.]]

In [[computing]], a '''denial-of-service attack''' ('''DoS attack''') is a [[cyberattack]] in which the perpetrator seeks to make a machine or network resource unavailable to its intended [[user (computing)|users]] by temporarily or indefinitely disrupting [[network service|services]] of a [[host (network)|host]] connected to a [[Computer network|network]]. Denial of service is typically accomplished by [[Flooding (computer networking)|flooding]] the targeted machine or resource with superfluous requests in an attempt to overload systems and prevent some or all legitimate requests from being fulfilled.<ref>{{cite web |date=6 February 2013 |title=Understanding Denial-of-Service Attacks |url=https://www.cisa.gov/news-events/news/understanding-denial-service-attacks |access-date=26 May 2016 |publisher=US-CERT}}</ref> The range of attacks varies widely, spanning from inundating a server with millions of requests to slow its performance, overwhelming a server with a substantial amount of invalid data, to submitting requests with an illegitimate [[IP address]].<ref>{{Cite journal |last1=Elleithy |first1=Khaled |last2=Blagovic |first2=Drazen |last3=Cheng |first3=Wang |last4=Sideleau |first4=Paul |date=2005-01-01 |title=Denial of Service Attack Techniques: Analysis, Implementation and Comparison |url=https://digitalcommons.sacredheart.edu/computersci_fac/52 |journal=School of Computer Science & Engineering Faculty Publications}}</ref>

In a '''distributed denial-of-service attack''' ('''DDoS attack'''), the incoming traffic flooding the victim originates from many different sources. More sophisticated strategies are required to mitigate this type of attack; simply attempting to block a single source is insufficient as there are multiple sources.<ref>{{Cite web|date=2021-01-13|title=What is a DDoS Attack? - DDoS Meaning|url=https://usa.kaspersky.com/resource-center/threats/ddos-attacks|access-date=2021-09-05|website=Kaspersky |language=en}}</ref><ref>{{Cite web|title=What is a DDoS Attack?|url=https://www.cloudflare.com/en-gb/learning/ddos/what-is-a-ddos-attack/|access-date=2024-12-04|website=Coudflare |language=en}}</ref>  A DDoS attack is analogous to a group of people crowding the entry door of a shop, making it hard for legitimate customers to enter, thus disrupting trade and losing the business money. Criminal perpetrators of DDoS attacks often target sites or services hosted on high-profile [[web server]]s such as [[bank]]s or [[credit card]] [[payment gateway]]s. [[Revenge]] and [[blackmail]],<ref>{{cite web |last1=Prince |first1=Matthew |author-link=Matthew Prince |date=25 April 2016 |title=Empty DDoS Threats: Meet the Armada Collective |url=https://blog.cloudflare.com/empty-ddos-threats-meet-the-armada-collective/ |access-date=18 May 2016 |website=CloudFlare}}</ref><ref>{{cite web|url=http://www.interpacket.com/42882/brand-com-victim-blackmail-attempt-says-president-mike-zammuto/ |title=Brand.com President Mike Zammuto Reveals Blackmail Attempt|date=5 March 2014|archive-url=https://web.archive.org/web/20140311070205/http://www.interpacket.com/42882/brand-com-victim-blackmail-attempt-says-president-mike-zammuto/|archive-date=11 March 2014}}</ref><ref>{{cite web|url=http://dailyglobe.com/61817/brand-coms-mike-zammuto-discusses-meetup-com-extortion/|title=Brand.com's Mike Zammuto Discusses Meetup.com Extortion|date=5 March 2014|archive-url=https://web.archive.org/web/20140513044100/http://dailyglobe.com/61817/brand-coms-mike-zammuto-discusses-meetup-com-extortion/|archive-date=13 May 2014|url-status=dead}}</ref> as well as [[hacktivism]],<ref name=":1">{{cite web |last=Halpin |first=Harry |date=2010-12-17 |title=The Philosophy of Anonymous |url=http://www.radicalphilosophy.com/article/the-philosophy-of-anonymous |access-date=2013-09-10 |publisher=Radicalphilosophy.com}}</ref> can motivate these attacks.