An adversary may execute a flooding attack using XML messages with the intent to deny legitimate users access to a web service. These attacks are accomplished by sending a large number of XML based requests and letting the service attempt to parse each one. In many cases this type of an attack will result in a XML Denial of Service (XDoS) due to an application becoming unstable, freezing, or crashing. XDoS is most closely associated with web services, SOAP, and Rest, because remote service requesters can post malicious XML payloads to the service provider designed to exhaust the service provider's memory, CPU, and/or disk space. The main weakness in XDoS is that the service provider generally must inspect, parse, and validate the XML messages to determine routing, workflow, security considerations, and so on. It is exactly these inspection, parsing, and validation routines that XDoS targets. This attack exploits the loosely coupled nature of web services, where the service provider has little to no control over the service requester and any messages the service requester sends.
Term: XML Denial of Service (XML DoS)
Likelihood Of Attack
The table below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
Meta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.
Detailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.
Survey the target: Using a browser or an automated tool, an attacker records all instance of web services to process XML requests.
Use an automated tool to record all instances of URLs to process XML requests.
Use a browser to manually explore the website and analyze how the application processes XML requests.
An adversary crafts input data that may have an adverse effect on the operation of the web service when the XML data sent to the service.
Launch a resource depletion attack: The attacker delivers a large number of XML messages to the target URLs found in the explore phase at a sufficiently rapid rate. It causes denial of service to the target application.
Send a large number of crafted XML messages to the target URL.
The target must receive and process XML transactions.
An adverssary must possess the ability to generate a large amount of XML based messages to send to the target service.
Denial of service
A large amount of data is passed to the XML parser possibly making it crash or otherwise unavailable to end users.
The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Design: Build throttling mechanism into the resource allocation. Provide for a timeout mechanism for allocated resources whose transaction does not complete within a specified interval.
Implementation: Provide for network flow control and traffic shaping to control access to the resources.
Consider the case of attack performed against the createCustomerBillingAccount Web Service for an online store. In this case, the createCustomerBillingAccount Web Service receives a huge number of simultaneous requests, containing nonsense billing account creation information (the small XML messages). The createCustomerBillingAccount Web Services may forward the messages to other Web Services for processing. The application suffers from a high load of requests, potentially leading to a complete loss of availability the involved Web Service.
A Related Weakness relationship associates a weakness with this attack pattern. Each association implies a weakness that must exist for a given attack to be successful. If multiple weaknesses are associated with the attack pattern, then any of the weaknesses (but not necessarily all) may be present for the attack to be successful. Each related weakness is identified by a CWE identifier.