[56031] in cryptography@c2.net mail archive
Re: Spammer using Graphical Steganography
daemon@ATHENA.MIT.EDU (Damien Miller)
Wed Oct 25 19:28:03 2006
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Thu, 26 Oct 2006 04:21:29 +1000 (EST)
From: Damien Miller <djm@mindrot.org>
To: Bill Stewart <bill.stewart@pobox.com>
Cc: cryptography@metzdowd.com
In-Reply-To: <6.2.1.2.0.20061023153540.04153830@pop.idiom.com>
On Mon, 23 Oct 2006, Bill Stewart wrote:
> Spammers have been including images in their email to evade anti-spammers.
> Anti-spammers have been using OCR to identify spammy words in images.
> Spammers have recently come up with tricks to work around OCRs,
> by doing steganography with animated GIF images.
> One approach they're taking is to build the real image progressively,
> first drawing a background, then drawing parts of the image
> (one spammer uses transparent pixels to do parts of it, showing dark parts of
> background),
> then waiting a long time and drawing a blank page in case anything's checking
> the final image.
IMO this isn't stego, more like a CAPCHA.
-d
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