The STRIDE Threat Model
When you are considering threats, it is useful to ask questions such as these:
- How can an attacker change the authentication data?
- What is the impact if an attacker can read the user profile data?
- What happens if access is denied to the user profile database?
You can group threats into categories to help you formulate these kinds of pointed questions. One model you may find useful is STRIDE, derived from an acronym for the following six threat categories:
- Spoofing identity. An example of identity spoofing is illegally accessing and then using another user's authentication information, such as username and password.
- Tampering with data. Data tampering involves the malicious modification of data. Examples include unauthorized changes made to persistent data, such as that held in a database, and the alteration of data as it flows between two computers over an open network, such as the Internet.
- Repudiation. Repudiation threats are associated with users who deny performing an action without other parties having any way to prove otherwise—for example, a user performs an illegal operation in a system that lacks the ability to trace the prohibited operations. Nonrepudiation refers to the ability of a system to counter repudiation threats. For example, a user who purchases an item might have to sign for the item upon receipt. The vendor can then use the signed receipt as evidence that the user did receive the package.
- Information disclosure. Information disclosure threats involve the exposure of information to individuals who are not supposed to have access to it—for example, the ability of users to read a file that they were not granted access to, or the ability of an intruder to read data in transit between two computers.
- Denial of service. Denial of service (DoS) attacks deny service to valid users—for example, by making a Web server temporarily unavailable or unusable. You must protect against certain types of DoS threats simply to improve system availability and reliability.
- Elevation of privilege. In this type of threat, an unprivileged user gains privileged access and thereby has sufficient access to compromise or destroy the entire system. Elevation of privilege threats include those situations in which an attacker has effectively penetrated all system defenses and become part of the trusted system itself, a dangerous situation indeed.