Denial- of- service attack - Wikipedia. In computing, a denial- of- service attack (Do. S attack) is a cyber- attack where the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connected to the Internet. Denial of service is typically accomplished by 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.[1]In a distributed denial- of- service attack (DDo. S attack), the incoming traffic flooding the victim originates from many different sources. This effectively makes it impossible to stop the attack simply by blocking a single source. A Do. S or DDo. S attack is analogous to a group of people crowding the entry door or gate to a shop or business, and not letting legitimate parties enter into the shop or business, disrupting normal operations. Criminal perpetrators of Do. S attacks often target sites or services hosted on high- profile web servers such as banks or credit cardpayment gateways. Luke Plunkett. Luke Plunkett is a Contributing Editor based in Canberra, Australia. He has written a book on cosplay, designed a game about airplanes, and also runs. The Speakers of DEF CON 25. Speaker Index. 0 0ctane 0x00string A Aleph-Naught-Hyrum Anderson Ayoul3 Dor Azouri. Revenge, blackmail[2][3][4] and activism[5] can motivate these attacks. History[edit]This section needs expansion. You can help by adding to it.(July 2. Court testimony shows that the first demonstration of Do. S attack was made by Khan C. Smith in 1. 99. 7 during a DEF CON event disrupting Internet access to the Las Vegas Strip for over an hour and the release of sample code during the event led to the online attack of Sprint, Earth. Link, E- Trade, and other major corporations in the year to follow.[6]Denial- of- service attacks are characterized by an explicit attempt by attackers to prevent legitimate users of a service from using that service. There are two general forms of Do. In computing, a denial-of-service attack (DoS attack) is a cyber-attack where the perpetrator seeks to make a machine or network resource unavailable to its intended. S attacks: those that crash services and those that flood services. The most serious attacks are distributed.[7]Distributed Do. S[edit]A distributed denial- of- service (DDo. S) is a cyber- attack where the perpetrator uses more than one unique IP address, often thousands of them. The incoming traffic flooding the victim originates from many different sources. This effectively makes it impossible to stop the attack simply by using ingress filtering. It also makes it very difficult to distinguish legitimate user traffic from attack traffic when spread across so many points of origin. As an alternative or augmentation of a DDo. S, many attacks involve forging of IP sender addresses (IP address spoofing) also so that the location of the attacking machines cannot easily be identified and defeated. The scale of DDo. S attacks has continued to rise over recent years, by 2. Application layer attacks[edit]An application layer DDo. S attack (sometimes referred to as layer 7 DDo. S attack) is a form of DDo. S attack where attackers target the application layer of the OSI model.[1. The attack over- exercises specific functions or features of a website with the intention to disable those functions or features. This application- layer attack is different from an entire network attack, and is often used against financial institutions to distract IT and security personnel from security breaches.[1. As of 2. 01. 3, application layer DDo. S attacks represent 2. DDo. S attacks.[1. According to research by the company Akamai, there have been "5. Q4 2. 01. 3 to Q4 2. Q3 2. 01. 4 over Q4 2. Application layer[edit]The Open Systems Interconnection (OSI) model (ISO/IEC 7. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO). The model groups similar communication functions into one of seven logical layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error- free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer. In the OSI model, the definition of its application layer is narrower in scope. The OSI model defines the application layer as being the user interface. The OSI application layer is responsible for displaying data and images to the user in a human- recognizable format and to interface with the presentation layer below it. Method of attack[edit]An application layer DDo. S attack is done mainly for specific targeted purposes, including disrupting transactions and access to databases. It requires less resources and often accompanies network layer attacks.[1. An attack is disguised to look like legitimate traffic, except it targets specific application packets.[1. The attack on the application layer can disrupt services such as the retrieval of information or search function[1. In order to be deemed a distributed denial of service attack, more than around 3–5 nodes on different networks should be used; using fewer than 3–5 nodes qualifies as a Denial- of- service attack and not a DDo. S.[1. 1][1. 6]Advanced persistent Do. S[edit]An advanced persistent Do. S (APDo. S) is more likely to be perpetrated by an advanced persistent threat (APT): actors who are well- resourced, exceptionally skilled and have access to substantial commercial grade computer resources and capacity. APDo. S attacks represent a clear and emerging threat needing specialised monitoring and incident response services and the defensive capabilities of specialised DDo. S mitigation service providers. This type of attack involves massive network layer DDo. S attacks through to focused application layer (HTTP) floods, followed by repeated (at varying intervals) SQLi and XSS attacks.[1. Typically, the perpetrators can simultaneously use from 2 to 5 attack vectors involving up to several tens of millions of requests per second, often accompanied by large SYN floods that can not only attack the victim but also any service provider implementing any sort of managed DDo. S mitigation capability. These attacks can persist for several weeks- the longest continuous period noted so far lasted 3. This APDo. S attack involved approximately 5. Attackers in this scenario may (or often will) tactically switch between several targets to create a diversion to evade defensive DDo. S countermeasures but all the while eventually concentrating the main thrust of the attack onto a single victim. In this scenario, threat actors with continuous access to several very powerful network resources are capable of sustaining a prolonged campaign generating enormous levels of un- amplified DDo. S traffic. APDo. S attacks are characterised by: advanced reconnaissance (pre- attack OSINT and extensive decoyed scanning crafted to evade detection over long periods)tactical execution (attack with a primary and secondary victims but focus is on primary)explicit motivation (a calculated end game/goal target)large computing capacity (access to substantial computer power and network bandwidth resources)simultaneous multi- threaded OSI layer attacks (sophisticated tools operating at layers 3 through 7)persistence over extended periods (using all the above into a concerted, well managed attack across a range of targets[1. Denial- of- service as a service[edit]Some vendors provide so- called "booter" or "stresser" services, which have simple web- based front ends, and accept payment over the web. Marketed and promoted as stress- testing tools, they can be used to perform unauthorized denial- of- service attacks, and allow technically unsophisticated attackers access to sophisticated attack tools without the need for the attacker to understand their use.[1. Symptoms[edit]The United States Computer Emergency Readiness Team (US- CERT) has identified symptoms of a denial- of- service attack to include: [2. Do. S attack is considered an e- mail bomb). Additional symptoms may include: disconnection of a wireless or wired internet connectionlong- term denial of access to the web or any internet services. If the attack is conducted on a sufficiently large scale, entire geographical regions of Internet connectivity can be compromised without the attacker's knowledge or intent by incorrectly configured or flimsy network infrastructure equipment. Attack techniques[edit]A wide array of programs are used to launch Do. S- attacks. Attack tools[edit]In cases such as My. Doom the tools are embedded in malware, and launch their attacks without the knowledge of the system owner.
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