Block a specific file

In article , mimiseh wrote: : Is there a way to block specific files from a router. Thanks.

Which model, which IOS version, which feature set, and block from being transported by which mechanism? Also, is the blocking to be done by file name, or by file content? If by file content, then is identification of the files a simple matter, or is what you are asking for really a form of virus checking complete with polymorphism and different kinds of compression algorithms and so on?