The RISKS Digest
Volume 9 Issue 65

Friday, 2nd February 1990

Forum on Risks to the Public in Computers and Related Systems

ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

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The C3 legacy, Part 2: a SAGE beginning
Les Earnest
Sendmail Flaw
Geoffrey H. Cooper
Filing 1040 Electronically
Bill Murray
Predicting Problems
David desJardins
Airbus crash
Dave Morton
The Trojan horse named `AIDS' revisited
Info on RISKS (comp.risks)

The C3 legacy, Part 2: a SAGE beginning

Les Earnest <LES@SAIL.Stanford.EDU>
01 Feb 90 2101 PST
Thanks to for pinning down my half-remembered
quotation in the preceding segment (RISKS 9.60):
> The actual quote is "Those who cannot remember the past are condemned
> to repeat it." from George Santayana's "The Life of Reason".

The grandfather of all command-control-communication (C3) systems was an
air defense system called SAGE, a rather tortured acronym for Semi-
Automatic Ground Environment.  As I reported earlier in RISKS 8.74, some of
the missles that operated under SAGE had a serious social problem:  they
tended to have inadvertent erections at inappropriate times.  A more
serious problem was that SAGE, as it was built, would have worked only in
peacetime.  That seemed to suit the Air Force just fine.

SAGE was designed in the mid to late 1950s, primary by MIT Lincoln Lab,
with follow-up development by IBM and by nonprofits System Development
Corp. and Mitre Corp.  The latter two were spun off from RAND and MIT,
respectively, primarily for this task.

SAGE was clearly a technological marvel for its time, employing digitized
radar data, long distance data communications via land lines and
ground-air radio links, the largest computer (physically) built before or
since, a special-purpose nonstop timesharing system, and a large
collection of interactive display terminals.  SAGE was necessarily
designed top-down because there had been nothing like it before — it was
about 10 years ahead of general purpose timesharing systems and 20 years
ahead of personal computers and workstations.

While the designers did an outstanding job of solving a number of
technical problems, SAGE would have been relatively useless as a defense
system if a manned bomber attack had occurred for the following reasons.

1. COUNTERMEASURES.  Each SAGE system was designed to automatically track
   aircraft within a certain geographic area based on data from several
   large radars.  While the system worked well under peacetime conditions,
   an actual manned bomber attack would likely have employed active radar
   jamming, radar decoys, and other countermeasures.  The jamming would
   have effectively eliminated radar range information and would even have
   made azimuth data imprecise, which meant that the aircraft tracking
   programs would not have worked.  In other words, this was a air defense
   system that was designed to work only in peacetime!
   (Some "Band-aids" were later applied to the countermeasures vulnerability
   problem, but a much simpler system would have worked better under expected
   attack conditions.)

2. HARDENING.  Whereas MIT had strongly recommended that the SAGE computers
   and command centers be put in hardened, underground facilities so that
   they could at least survive near misses, the "bean counters" in the Pentagon
   decided that this would be too expensive.  Instead, they specified
   above-ground concrete buildings without windows.  This was, of course,
   well suited to peacetime use.

3. PLACEMENT.  While the vulnerabilities designed into SAGE by MIT and the
   Pentagon made it relatively ineffective as a defense system, the Air
   Defense Command added a finishing blunder by siting most of the SAGE
   computer facilities in such a way that they would be bonus targets!
   This was an odd side effect of military politics and sociology, as
   discussed below.

In the 1950s, General Curtis Lemays's Strategic Air Command consistently
had first draw on the financial resources of the Defense Department.  This
was due to the ongoing national paranoia regarding Soviet aggression and
some astute politicking by Lemay and his supporters.  One thing that Lemay
insisted on for his elite SAC bases was that they have the best Officers
Clubs around.

MIT had recommended that the SAGE computer facilities be located remotely,
away from both cities and military bases, so that they would not be bonus
targets in the event of an attack.  When the Air Defense Command was
called upon to select SAGE sites, however, they realized that their people
would not enjoy being assigned to the boondocks, so they decided to put
the SAGE centers at military bases instead.

Following up on that choice, the Air Defense Command looked for military
bases with the best facilities, especially good O-clubs.  Sure enough, SAC
had the best facilities around, so they put many of the SAGE sites on SAC
bases.  Given that SAC bases would be prime targets in any manned bomber
attack, the SAGE centers thus became bonus targets that would be destroyed
without extra effort.  Thus the peacetime lifestyle interests of the
military were put ahead of their defense responsibilities.

SAGE might be regarded as successful in the sense that no manned bomber
attack occurred during its life and that it might have served as a
deterrant to those considering an attack.  There were reports that the
Soviet Union undertook a similar experimental development in the same time
period, though that story may have been fabricated by Air Force
intelligence units to help justify investment in SAGE.  In any case, the
Russians didn't deploy such a system, either because they lacked the
capability to build a computerized, centralized "air defense" system such
as SAGE or had the good sense not to expend their resources on such a
vulnerable kludge.

(Next segment: command-control catches on.)

    -Les Earnest (

Sendmail Flaw

Geoffrey H. Cooper <>
Fri, 2 Feb 90 14:35:37 PST
The sendmail problem to which our moderator frequently refers is
actually a design problem in the SMTP protocol (that sendmail
implements) and so is well within the domain of RISKS discussions.
Especially since the design problem has been recognized since at least
1983, but SMTP is so entrenched that the problem has never been fixed.

The way in which SMTP sends a message is, roughly:

    1. Send message headers to server, etc. & get responses
    2. Send DATA keyword to server & get affirmative response
    3. Send entire message to server with no response
    4. Send "." to Server

[5] is the problem.  At any given time during [5], there are two
possibilities.  Either the server has crashed and will never send an
answer, or the server is still in the process of transmitting the mail.

There is NO WAY for the sender to tell the difference between these
two possibilities.  This is because:

    a. SMTP presumes that TCP is reliable, so it doesn't allow
       the sender to retransmit anything.  Hence, the sender can't
       send any data during the wait in [5] to find out if the
       server is still alive.

    b. TCP, to be efficient for long lived connections, does
       not guarantee continual monitoring of the connection.  If
       TCP has no data to send, it never sends any data (except
       for the Berkeley-derived keep-alive option, which are not
       part of the TCP spec, but see below).

    c. EVEN IF TCP did monitor the connection, the SMTP process
       could die or go into an infinite loop without resetting
       the TCP connection.  (You can't catch this
       case: Halting Problem).  I can vaguely remember
       hearing of this happening in 1983.

I truly believe this problem is unsolvable, without changing SMTP.  The
Programming Marines, who build and sell systems must solve it anyway.  Or
alleviate it, anyway.

The ad-hoc solution is to set a timeout; assume the message takes no more than
time T to process by the server, so if the sender waits for 2T or so, the
server must have crashed.  This helps, but it clearly doesn't solve the
problem, since the sender has no metric by which to judge T except the length
of the message.

For example, a message transmitted to a Large, Risky Mailing List might take an
order of magnitude longer to process than a simple user-to-user message.
Hence, it is likely that messages to large mailing lists will tend to fail with
the sender timing out and resetting the connection; this condition is noticed
by the server AFTER transmitting at least part of the message.  The sender
later retries, so you get multiple messages.  Very many messages, if you are
unlucky, or its a Monday or you moderate a very large and risky mailing list.

(BTW, it was decided in SMTP's design that it was better to have multiple
messages than to have messages get lost, so it is not considered acceptable for
the SMTP server to queue the message but not deliver it during the pause in

The general problem: building functionality on top of a "reliable
system" does not GUARANTEE that the result is reliable.  The
reliability must, in some way, be verified by the topmost level.

Hence, you balance your bank statement to make sure your checks (
were really cashed shortly after you sent them off, and you look for cancel
checks if you get a red notice from a bill you sent off.

J. Saltzer, D. Reed, D. Clark, "End-to-End Arguments in System Design",
Proc. IEEE, April 1981.

- Geof

     [Well, on RISKS-9.64 I removed all of the offending addresses and
     I did not get any reports of multiples.  So, here goes RISKS-9.65.  PGN]

Filing 1040 Electronically

Fri, 2 Feb 90 17:47 EST
It is now possible for you to file your income tax return electronically.  Yes,
you.  Of course the IRS will not accept it directly from you; they only deal
with "tax preparers' like H&R Block, the owners of CompuServe.  Not to worry.
There are value-added re-sellers who will accept your return from you, check it
and forward it to the IRS.  I have seen ads now from two different such
re-sellers: "Nelco" and "Nexus Direct."

PGN's misgivings to the contrary notwithstanding, it is not likely to open up
the IRS's computers to tampering by taxpayers.  From their point of view it is
as safe as having you send it to them by snailmail and a lot cheaper than
key-entering it themselves.

From the taxpayers' point of view, it is a great deal safer than putting
it in the snailmail and having it transcribed by a temp at the IRS.  Of
course, a copy of your return can end up in the computers of the
services.  On the other hand, that happens whenever you deal with a tax
preparer.  That has only marginally impacted the success of H&RB.

Incidentally, when you file with H&RB, or any number of other preparers,
they offer to give you your refund on the spot.  It is really in the
form of a loan, but the loan is re-paid directly to them by the IRS.
The IRS likes this arrangement because they can pay the refund by
EFT/EDI.  Not only do they not handle the paper return, but they do not
have to prepare a check for the refund.   It is almost as if the IRS has
opened thousands of offices across the country where they will prepare
your return for you and give you your refund on the spot.  Of course,
since it is for-profit, it may be a little more efficient.

Who pays?  Well who always pays?  At least there are some choices.

How about it H&RB?  How long will it be before I can "GO 1040" on

William Hugh Murray, Fellow, Information System Security, Ernst & Young
2000 National City Center Cleveland, Ohio 44114
21 Locust Avenue, Suite 2D, New Canaan, Connecticut 06840

Predicting Problems

David desJardins <desj%idacrd@Princeton.EDU>
Fri, 2 Feb 90 01:05:48 EST
Bob Munck <> writes:
<> While the software had been rigorously tested in laboratory
<> environments before it was introduced, the unique combination of
<> events that led to this problem   couldn't be   predicted.
> Don't they mean "wasn't"?  The rest of the report seems (to me) to
> be reasonably detailed, well explained, and apparently honest, but
> this one little dissemblance ruins the whole thing.  Is there any
> justification for the assertion that the prediction was (and is)
> _impossible_ in these circumstances?

   I noticed this too.  On reflection, though, I'm sort of glad that they said
it this way.  Of course this error could have been predicted.  Any particular
error could be predicted, if the right person looked at it at the right time.
But what *is* impossible is to predict all errors, all of the time, with
probability 1.  So, if you interpret the above statement above as, "The event
occurred randomly in a situation where the probability of such errors could not
be reduced to zero," then I think it is a reasonable description of the truth.

   Certainly it is a better reaction than the other common thing that one sees
in these press statements, which is something like, "Steps are being taken to
ensure that no similar outage can ever occur again."  This is an unrealistic
and false reaction which would cause me, at least, far more concern than the
AT&T reaction.  Of course they will try to prevent such problems.  But it is
equally obvious that the probability of such events will remain positive.

   — David desJardins

Airbus crash

Dave Morton <dave@ecrcvax.UUCP>
Fri, 2 Feb 90 09:22:30 +0100
Coming back from London about a year ago I was seated next to a pilot
from a Munich based company who flew 757s. He'd overshot his flying time
and was heading back to Munich from Kenya over London. We talked about the
Airbus crash and it seems that in pilot circles it was attributed to the
fact that the older Airbus machines had Rolls-Royce engines. It seems that
when given full power they reacted about 3 seconds faster that those on
the A320. In his opinion these three seconds were vital. Needless to say,
the A320 pilot was familiar with the older model(s) and this may have played
a role in his judgement. On a side note the pilot also mentioned that the
757, which also has the fly by wire system, sometimes "hangs". The only
way to get the electronics to function again is to power cycle the lot.

The Trojan horse named `AIDS' revisited (RISKS-9.55)

"Peter G. Neumann" <>
Fri, 2 Feb 90 15:58:21 EST
We reported earlier on the diskettes containing a destructive Trojan horse
program.  Something like 20,000 disks were mailed from London around 11
December 1989.  When executed, it trashed PCs in at least Britain, Norway,
Sweden, Belgium, Denmark and California.

Joseph W. Popp, 39, a zoologist from the Cleveland area, has been arrested in
Ohio on a federal fugitive warrant, and charged by Scotland Yard in London with
blackmail and extortion.  In court in Cleveland, Popp told U.S. Magistrate
Joseph W. Bartunek he is under a psychiatrist's care and must take drugs for a
mental condition.  The judge has scheduled psychiatric evaluation prior to any
further hearing.  Popp apparently (has/had?) worked for the World Health

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