EXE upload prevention

I need to implement EXE file upload prevention in my project in the same way as it is implemented in gmail (even if EXE file is within a password protected zip file, gmail is able to detect it). What开发者_如何转开发 approach should I follow?

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You can browse the contents of a zip file even if it is password protected.

If the zip file is password protected all you can do is to check file extensions. If not protected, you can check contents for executables (exe, scr): http://support.microsoft.com/kb/65122