This dissertation focuses on the forensic validation of computer evidence. It is a burgeoning field, by necessity, and there have been significant advances in the detection and gathering of evidence related to electronic crimes. What makes the computer forensics field similar to other forensic fields is that considerable emphasis is placed on the validity of the digital evidence. It is not just the methods used to collect the evidence that is a concern. What is also a problem is that perpetrators of digital crimes may be engaged in what is called anti-forensics. Digital forensic evidence techniques are deliberately thwarted and corrupted by those under investigation. In traditional forensics the link between evidence and perpetrator's actions is often straightforward: a fingerprint on an object indicates that someone has touched the object. Anti-forensic activity would be the equivalent of having the ability to change the nature of the fingerprint before, or during the investigation, thus making the forensic evidence collected invalid or less reliable. This thesis reviews the existing security models and digital forensics, paying particular attention to anti-forensic activity that affects the validity of data collected in the form of digital evidence. This thesis will build on the current models in this field and suggest a tentative first step model to manage and detect possibility of anti-forensic activity. The model is concerned with stopping anti-forensic activity, and thus is not a forensic model in the normal sense, it is what will be called a “meta-forensic” model. A meta-forensic approach is an approach intended to stop attempts to invalidate digital forensic evidence. This thesis proposes a formal procedure and guides forensic examiners to look at evidence in a meta-forensic way.

In order to keep shared access computers secure and stable system administrators resort to locking down the computing environment in order to prevent intentional and unintentional damage by users. Skilled attackers are often able to break out of locked down computing environments and intentionally misuse shared access computers. This misuse has resulted in cases of mass identity theft and fraud, some of which have had an estimated cost ranging in millions. In order to determine if it is possible to break out of locked down computing environments an assessment method is required. Although a number of vulnerability assessment techniques exist, none of the existing techniques are sufficient for assessing locked down shared access computers. This is due to the existing techniques focusing on traditional, application specific, software vulnerabilities. Break out path vulnerabilities (which are exploited by attackers in order to break out of locked down environments) differ substantially from traditional vulnerabilities, and as a consequence are not easily discovered using existing techniques. Ontologies can be thought of as a modelling technique that can be used to capture expert knowledge about a domain of interest. The method for discovering break out paths in locked down computers can be considered expert knowledge in the domain of shared access computer security. This research proposes an ontology based assessment process for discovering break out path vulnerabilities in locked down shared access computers. The proposed approach is called the ontological lockdown assessment process. The ontological lockdown assessment process is implemented against a real world system and successfully identifies numerous break out path vulnerabilities.