Vulnerability Development mailing list archives
Re: Obfuscated shellcode
From: "Don Parker" <dparker () rigelksecurity com>
Date: Sun, 1 Feb 2004 16:57:50 -0500 (EST)
Hi Aaron, well agreed any IDS worth it's salt will detect a NOOP sled. I have however seen the signatures firsthand of some major vendors and they all go for very generic stuff such as the NOOP times n amount, and perhaps port matching. That is it, literally. Also drawing on my work with some large entities I know firsthand that the rollout of some patches can be very slow, thereby leaving open a large window of opportunity for a munged egg to get through. Hence my question on using an obfuscated egg to slip past the IDS. Cheers, Don ------------------------------------------- Don Parker, GCIA Intrusion Detection Specialist Rigel Kent Security & Advisory Services Inc www.rigelksecurity.com ph :613.249.8340 fax:613.249.8319 -------------------------------------------- On Feb 1 , Aaron Turner <aturner () pobox com> wrote: Don, While most IDS's will detect a NOOP sled, any IDS worth it's salt which has a signature for an exploit won't rely on it. Rather it will use something unique to the exploit which can't (at least easily) changed to avoid detection. Also, in my experiance most corporations update their signatures about as often as feasible (a combination of how often the IDS vendor updates the signatures and how easy it is to push the update to the sensors). Any organization which isn't using the latest signature set is wasting their effort and $$$. Ie, if you have to carefully manage your signature set and delay updating your sensors because things might horribly break without a way to manage that risk, then you should find another IDS vendor. -- Aaron Turner <aturner at pobox.com|synfin.net> http://synfin.net/ They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety. -- Benjamin Franklin All emails are PGP signed; a lack of a signature indicates a forgery. On Sun, Feb 01, 2004 at 12:38:32PM -0500, Don Parker wrote:
Hello all, do any of you bother using obfuscated eggs during a pentest? I
ask here for I
got no responses elsewhere. Though changing the well known x90 sled to so
me other 1 byte
function that won't affect the egg won't work against a patched service i
t will, however
elude an IDS signature.
Quite a few large corporations may get updated signatures relatively quic
kly but, they
often do not patch for sometime due to baseline rollouts. Hence using an
obfuscated egg
to slip past the IDS. This technique is not new, but it is becoming more
well known.
There are some mitigaing factors here which could affect this such as app
lication layer
firewalls and the such. I would however be interested in your thoughts on
this. I have
not seem much discussion anywhere on this topic.
UNKNOWN
Current thread:
- Obfuscated shellcode Don Parker (Feb 01)
- Re: Obfuscated shellcode Aaron Turner (Feb 01)
- Re: Obfuscated shellcode Karma (Feb 01)
- RE: Obfuscated shellcode Bojan Zdrnja (Feb 01)
- <Possible follow-ups>
- Re: Obfuscated shellcode Don Parker (Feb 01)
- Re: Obfuscated shellcode Don Parker (Feb 01)
- Re: Obfuscated shellcode Aaron Turner (Feb 01)