Link to ModThis mod adds three group permissions that allow/deny users from reading normal/sticky/digest topics. Listing of topic is unaffected.
Own topics are not affected.
Attachments are not affected, however if you cannot read a topic then you can't see links to its attachments.
If a user cannot access a board, read permissions cannot help it.
Digest topic is supported by Topic Digest mod and is optional. This is an independent mod.
Sticky digest topics are treated as sticky topic for read permission if sticky is enabled.
Check access for recent posts or last posts, but not search result (that only shows partial posts anyway). Search can be controlled with another permission.
Error messages can be customised in modifications.english.php