OT: ImageInfo or some other tool to detect Animated Gifs.

[Duncan, Brian M.]

> I looked at about a dozen animated GIFs and I see one common
> thing. They have the text string "NETSCAPE2.0" (without the quotes).
> You would have to add something to the magic that the file
> command uses(mine is /usr/share/magic), and then you could
> ban that filetype in MailScanner.
> I would check as many animated GIF's as you can before you
> try this to make sure that string is there.
> I don't see that string in my magic file, so it shouldn't
> conflict with anything, but I can't be sure about false positives.
>
> Or you could just ban all gif images, if that will fly with
> your users.
>
>

I don't have the option to ban all GIF images. 

I just started looking through the SpamAssasin mail list and see someone
has commented on animated GIF's.

> A simple way to block these images would
> be to scan the GIF for offset frames. I don't think there is any valid

> GIF which makes use of these techniques

I am guessing that GIF images that do not contain offset frames would
then be static and would have a better
Chance of being OCR'ed correctly.  Attached logo's for users messages is
really the reason for me to allow inline images.

So if there was a way to detect GIF's that contain offset frames that
would be great. (Through something like ImageInfo.pm)



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