From owner-freebsd-security Tue Dec 11 22:56: 1 2001 Delivered-To: freebsd-security@freebsd.org Received: from poontang.schulte.org (poontang.schulte.org [209.134.156.197]) by hub.freebsd.org (Postfix) with ESMTP id 8D27537B405 for ; Tue, 11 Dec 2001 22:55:58 -0800 (PST) Received: from tarmap.schulte.org (tarmap.schulte.org [209.134.156.198]) by poontang.schulte.org (Postfix) with ESMTP id 56B83D160D; Wed, 12 Dec 2001 00:55:57 -0600 (CST) Message-Id: <5.1.0.14.0.20011212004626.03242638@pop.schulte.org> X-Sender: schulte@pop.schulte.org X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Wed, 12 Dec 2001 00:55:56 -0600 To: Landon Stewart , security@FreeBSD.ORG From: Christopher Schulte Subject: Re: MD5 sum checking for installed binaries to check for intrusion or root kits... In-Reply-To: <3C16FB8C.9020908@uniserve.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org At 10:39 PM 12/11/2001 -0800, Landon Stewart wrote: >They could have done who knows what to whatever system(s) they wanted >to. Without someone saying "reformat the machines or reinstall" because >thats the obvious answer, is there a way to check which files differ from >the size they should be and have the correct MD5 sum than they should or >is this asking too much? With no point of reference on 'good state', there's not a lot that can be done. Your previous admins may have legitimately patched things, installed non-standard binaries, or otherwise altered the system from what you'd be able to use as a reference. Even if you could match md5sums, there's many other ways by which a person could install a back door. For example, something as simple as an entry in inetd.conf which serves a root shell upon tcp port connection would not show up in a binary-only md5 scan. Install tripwire (or some custom checksum monitoring system) from the beginning of the OS install for best results. I know, not too much help now. :-( -- Christopher Schulte christopher@schulte.org http://noc.schulte.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message