Distributed Denial of Service (DDoS) attacks come in many guises. One of the more popular these days is the application-layer attack, sometimes called a layer seven attack, because it targets the top layer of the Open Systems Interconnection (OSI) model, which supports application and end-user processes.
Unlike volumetric attacks, which overwhelm networks quickly by consuming high levels of bandwidth, application-layer attacks are more subtle and insidious – and much more difficult to detect and block. Posing as legitimate application users, attackers target specific resources and services, sending repeated application requests that gradually increase in volume and eventually exhaust the ability of the resource to respond. Widely regarded as the deadliest kind of DDoS attack, application-layer attacks can inflict significant damage with a much lower volume of traffic than a typical volumetric attack, making them difficult to detect and mitigate proactively with traditional flow-based monitoring solutions. While service providers can detect and block volumetric attacks as well as larger application-layer attacks, smaller application attacks can easily escape detection in the large Internet Service Provider (ISP) backbone, while still being large enough to cause a problem for the enterprise network or data centre.
A Growing Threat
Application-layer attacks figure prominently in the DDoS threat landscape. HTTP and secure HTTPS services are targeted frequently, rendering them unavailable to legitimate requests. In fact, many business-critical applications are built on top of HTTP or HTTPS, making them vulnerable to this form of attack even though they may not look like traditional public web-based applications. For a bank or an online retailer that depends on its web presence to attract and serve customers, the impact can be catastrophic. Not only does the attack prevent the normal operation of the business, but it can also make a site invisible to search engines, or at least bump it from the front page of search results…Click here to read full article.
