"rlastar" <email@example.com> wrote in message
> My company save files with an unknown extension for security. When I
> an email (using gmail) with the file attached I save the file to a folder,
> automatically changes the extension to .zip
> It's definitely and IE8 issue as with Firefox it saves the file with our
> unknown extension.
> I've checked Internet options but can't find what setting is causing this
> Any help is appreciated.
IE uses "MIME Sniffing" if the content-type header and file extension can't
be used to figure out the type of file.
So, if these files are ZIP files as determined from the first 200 bytes of
the file, IE will give them the .ZIP file extension (this may also occur
with other file types that internally use ZIP compression, such as Office
2007 compressed documents). This is a security feature in IE - it's designed
to stop malicious attachments masquerading as something else.
Security by obscurity is not a good practice. It's pretty trivial to
determine the type of content of most files from the first few bytes, so
using "unknown" file extension just ends up making things more difficult for
humans but has little effect on software designed to figure out the file
type as you've found out.