From owner-freebsd-current Thu Sep 24 09:18:58 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id JAA24905 for freebsd-current-outgoing; Thu, 24 Sep 1998 09:18:58 -0700 (PDT) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from mailgw1.lmco.com (mailgw1.lmco.com [192.31.106.3]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id JAA24900 for ; Thu, 24 Sep 1998 09:18:56 -0700 (PDT) (envelope-from George.W.Dinolt@lmco.com) Received: from emss02g01.ems.lmco.com (relay2.ems.lmco.com [198.7.15.39]) by mailgw1.lmco.com (8.8.8/8.8.8) with ESMTP id KAA15522; Thu, 24 Sep 1998 10:18:45 -0600 (MDT) Received: from wdl1.wdl.lmco.com ([137.249.32.1]) by lmco.com (PMDF V5.1-10 #20543) with SMTP id <0EZS00MP9QN8CL@lmco.com>; Thu, 24 Sep 1998 10:18:45 -0600 (MDT) Received: from lmco.com by wdl1.wdl.lmco.com (SMI-8.6/WDL-5.0) id JAA12058; Thu, 24 Sep 1998 09:18:37 -0700 Date: Thu, 24 Sep 1998 09:18:36 -0700 From: "George W. Dinolt" Subject: Re: Limit 'ps' to show only user's processes To: Robert Watson Cc: Brian Tao , FREEBSD-CURRENT Message-id: <360A70DC.29BE32C5@lmco.com> Organization: Lockheed Martin Western Devlopment Labs MIME-version: 1.0 X-Mailer: Mozilla 4.05 [en] (X11; U; SunOS 5.5.1 sun4u) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit References: Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Hi: There was some work done in the 1970's and 1980's studying the kinds of things you are discussing in this thread. The work was known as 'covert channel' or 'information flow' analysis. Some of the work was done in the context of Multilevel Security although obviously the concepts apply to other systems as well. The basic idea was that a "low" user should not be able to determine "high" information by analyzing system behavior visible to the low user. (In addition, there was the hope that one could prevent a high user from signaling information to a low user via manipulations of the system resources visible to low users. (It should not be surprising that this sounds slightly convoluted.) If you are interested in this area you might find the section on Information Flow Analysis in Morrie Gasser's book {\bf Building a Secure Computer System} interesting. It gives a high level introduction to the area and some pointers to other work. Several of my colleagues and I have done covert channels analysis on systems. As you have pointed out, removing the channels entirely is often impossible and limiting the bandwidth to "reasonable" levels is difficult. The mechanisms needed to limit the bandwidth often interfere with other features the system is supposed to provide. -- Regards, George W. Dinolt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message