If the trust relationships between forests and domains are not regularly evaluated to determine whether they are still needed and justified, problems with authorisations can occur and information can leak out. It is also necessary to regularly check whether these relationships are of the correct type, especially with regard to whether a two-way trust relationship is really necessary and whether the security controls for such relationships are sufficient. In particular, if the Security Identifier (SID) filtration that is active by default is disabled, complex vulnerabilities may arise that are difficult to understand. The same applies if selective authentication is waived for trust relationships between forests.