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Date: Thu, 5 Sep 2002 11:33:21 -0700
From: Brian Hatch <secprog@ifokr.org>
To: Crispin Cowan <crispin@wirex.com>
Cc: Ben Mord <bmord@icon-nicholson.com>,
	"Webappsec Securityfocus.Com" <webappsec@securityfocus.com>,
	SECPROG Securityfocus <SECPROG@securityfocus.com>
Subject: Re: use of base image / delta image for automated recovery from
    attacks
Message-Id: <20020905183321.GH4340@ifokr.org>
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> Simple approxmation to this: make /usr a separate partion, and mount it=
=20
> read-only:
>=20
>    * The good news: attackers that want to trojan your software have to
>      reboot, at least.
>    * The bad news: administrators that want to update your software
>      have to reboot, at least.

No reboot is required, you just need to remount it:

	# mount -o remount,rw /usr

This requires root access, but presumably /usr is safe from non-root
users anyway.

Only way to disable this is to have the kernel compiled with something
that compartmentalizes capabilities (LIDS/etc on Linux for example) or to
remove CAP_SYS_ADMIN with lcap, which would definately require a reboot,
and possibly break some other functionatily to boot.  (Pun intended.  My
apologies.)

--
Brian Hatch                  "Are you expected?"
   Systems and               "No.  Dreaded."
   Security Engineer
www.hackinglinuxexposed.com

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