When you attempt to upload a file in WordPress that is not in the default list of acceptable file types, you will receive the following error: File type does not meet security guidelines. Try another. While there’s no admin-based tool for editing list of allowed file types, it’s not at all difficult to add your own or remove any existing.
Upload filetypes are checked by the function wp_check_filetype in wp-includes/functions.php. But we will add new file types to the file functions.php in our template due to upgrade WordPress.
Open your theme’s functions.php file and add this line somewhere between the <?php and ?>:
 

add_filter('upload_mimes', 'custom_upload_mimes');
function custom_upload_mimes ( $existing_mimes=array() ) {
// add your extension to the array
$existing_mimes['deb'] = 'application/x-deb';
// add as many as you like
// removing existing file types
unset( $existing_mimes['exe'] );
// add as many as you like
// and return the new full result
return $existing_mimes;
}

In this case I allowed upload .deb files and banned upload .exe files. List of MIME Types can be found here, or use google, if your file type is not in the list (e.g. deb or rpm file type).