ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel
  • »
  • Technology»
  • Internet & the Web

What is a Denial of Service (DOS) / DDOS Attack?

Updated on October 22, 2010

Early Denial of Service (DOS) attacks were considered games played by programmers to disable opponent’s memory. Today, DOS attacks are used to disable and disrupt services and cause company network outages. DOS and Distributed Denial of Service (DDOS) attacks are typically malicious in nature.

The purpose of DOS and DDOS attacks is simple: “to force a target system to become overloaded with activities that reduce its capacity to process legitimate tasks” (Janczewski & Colarik, 2005, p. 86). An example of a DOS attack is the 1987 Christmas Tree Exec worm (actually a Trojan horse) (Lilley, 2002). The Christmas Tree worm’s intent was not malicious. The Christmas Tree worm was used to draw a Christmas tree picture and email the picture to everyone in the user’s address book (Lilley, 2002). The Christmas Tree worm inadvertently used too many resources and forced many computers to shut down. This overutilization of resources prevented legitimate work from being performed on the computers infected by the Christmas Tree worm.

For large corporations with super computers, a DOS attack is often ineffective and a DDOS attack is the preferred denial of service attack. A DDOS attack has several stages. The first stage involves finding and prepping zombie computers. Zombie computers are computers used to carry out tasks. These zombie computers must first be compromised by the attacker. A compromised zombie computer can either be remotely controlled by the attacker or may be configured to perform a task at a specific date and time. Once the attacker has enough zombie computers under his control, he can use the zombie machines to simultaneously launch a DDOS attack against a specific target. This may result in thousands of zombies sending requests to a single web server, hence overwhelming the web server and rendering it unable to support normal traffic.

One of the most commonly used DOS and DDOS attacks is a SYN (Synchronize) Flood attack (Russell, 2000). The SYN Flood utilizes the TCP (Transmission Control Protocol) handshake mechanism. In computer network communications, TCP requires the client first send a SYN packet. The server then returns a SYN and ACK (Acknowledgement) packet. The server expects a return ACK packet from the client. The server leaves a socket open and reserves resources waiting for the client to send the ACK packet to complete the three part handshake. A SYN Flood attack takes advantage of the TCP handshake mechanism by sending a server thousands of SYN packets with a spoofed source address and never returning any ACK packets (Russell, 2000). This causes the server to tie up all resources by leaving thousands of sockets open waiting for ACK packets from clients. The utilization of zombie computers for a SYN Flood attack turns the attack into a DDOS and can easily overwhelm most servers.

SYN Flood

Syn Flood Example
Syn Flood Example

DOS and DDOS attacks are difficult to detect and are easy for attackers to use. Many tools are available via the Internet that help attackers setup DOS and DDOS attacks. One of the only effective mechanisms for detecting DOS and DDOS attacks is anomaly-based intrusion detection systems. Anomaly-based detection systems can detect unusual network activity, such as a flood of SYN packets and either alert a system administrator or automatically take action to prevent the attack.


Please check out one of my other articles on information security:

References

Janczewski, L., & Colarik, A. (2005). Managerial guide for handling cyber-terrorism and information warfare. Hershey, PA: Idea Group, Inc.

Lilley, P. (2002). Hacked, attacked and abused: digital crime exposed. Milford, CT: Kogan Page, Limited.

Russell, R. (2000). Hack proofing your e-commerce site: the only way to stop a hacker is to think like one. Rockland, MA: Syngress Publishing.

Comments

    0 of 8192 characters used
    Post Comment

    • Hello, hello, profile image

      Hello, hello, 8 years ago from London, UK

      Thank you for this important information. Where do you get this detection system?

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: "https://hubpages.com/privacy-policy#gdpr"

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)