The klez filter doesn't really try to find the Klez virus. Its more like an "EXE file in an attachment" filter. The checks aren't really correct, either.
The one I've got looks for a particular string and only in likely cases. It shouldn't be filtering *all* exe's unless they all have m!^TVqQAAMAAAAEAAAA//8AALgAAAAAAAAAQA! in the first 40 lines...
