From: H D Moore (fdlistdigitaloffense.net)
Date: Wed Jun 20 2007 - 09:19:49 CDT

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Agreed. The point was that IPS vendors have put a large amount of effort
into normalizing IIS-specific encodings, but fail to handle
Apache-specific quirks.

The note in RFC 2616, Section 4.1, refers to a single CRLF before the
Request-Line. Prepending multiple CRLFs or non-printable characters (as
coderman mentioned) falls outside of the RFC and I consider them
Apache-specific HTTP evasions.

Jamie has a good point about the PHP RFI signatures. Many IPS products
(sorry, I don't want to pick on any particular vendor) will look for a
http:// URL to detect RFI attacks. Replacing http with one of the other
protocol handlers (zip, ftp, file, smb on windows, etc) will evade many
of these signatures. The php://filter/resource trick is a nice hack for
evading existing signatures while still using a http URL for the included
PHP code.

-HD

On Wednesday 20 June 2007 08:50, 3APA3A wrote:
> You  simply  MUST  accept  the  risk  there  is always the way to
> bypass content  filtering. IPS like doesn't protect your network by
> itself. IPS is nothing, but a tool.

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