Trustlevels are a system that can be used to limit access to certain modules depending on where the file originates. It can be used to give trusted persons access to potentially hazardous modules like the CGI executable support module or the SQL-module.

Trustlevels work by setting the Builtin variables/Security: Security level variable of modules.

A request is initially assigned a trust level equal to the security level of the filesystem module from which it originates.

The request will only be able to pass through modules with an equal or lower security level than the request's trust level. Modules that has a higher security level will be ignored, like they were not even enabled.

If the request passes through a module with a lower security level than the request's trust level, the trust level will be lowered to the security level. If the request tries to pass through additional modules it will use the lowered trust level.

Example

CGI executable support - trust level 1
Pike tag - trust level 1
Filesystem - trust level 1
User Filesystem - trust level 0

User home pages, that are handled by the User Filesystem module may not, on the other hand, contain CGI scripts nor use the <pike> tag.