An improved system and approaches for protecting secured files when being used by an application (e.g., network browser) that potentially transmits the files over a network to unknown external locations are disclosed. According to one aspect, access to secured files is restricted so that unsecured versions of the secured files are not able to be transmitted over a network (e.g., the Internet) to unauthorized destinations. In one embodiment, in opening a file for use by a network browser, the network browser receives a secured (e.g., encrypted) version of the secured file when the destination location (e.g., destination address) for the network browser is not trusted, but receives an unsecured (e.g., unencrypted) version of the secured file when the destination location for the network browser is trusted. According to another aspect, processes operating on a computer system are monitored to determine destination locations, if any, of said processes, and then using such destination locations to determine whether to permit the processes to open files in a secure or unsecured manner.