A filtering method and apparatus for a portable electronic device such as a palmtop computer. The operating system's program registry is copied and then modified to direct all application data to a filter program such as a virus scanning filter program. If the filter program determines that the object is virus free, the copy of the program registry (filter registry) is queried by the filter program to determine the application program associated with the data object. The data object is then forwarded to the appropriate application program.