The Risks Digest

The RISKS Digest

Forum on Risks to the Public in Computers and Related Systems

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

Volume 6 Issue 54

Monday 4 April 1988


o Re: April Fool's Warning from Usenet
Gene Spafford
o Intolerant Fault-Tolerance
Jerome H. Saltzer
o How Computers Get Your Goat
o Old viruses
Jerry Leichter
o Re: Notifying users of security problems
Andy Goldstein
o The "previous account" referred to in RISKS-6.51
Les Earnest
o Just Another Unix Spoof
Paul Cudney
o Info on RISKS (comp.risks)

Re: April Fool's Warning from Usenet (RISKS-6.52)

Gene Spafford <>
4 Apr 88 23:34:57 GMT
In Risks 6.52, Cliff Stoll forwarded a posting on the Usenet about forged
articles.  He attributed it to me, and unfortunately either Cliff or Peter
trimmed most of the news header lines out.  Why was it unfortunate?  Because
the article was itself a forgery, and the headers exhibited all of the
indicators the posting warned were in bogus articles!

It was a marvelous joke except for the fact I've gotten about 40 mail
messages so far from people who didn't realize that it was a forgery.  Now
it shows up in Risks!

I am 99% certain who did it, and I can't wait for next April 1....

Gene Spafford
NSF/Purdue/U of Florida  Software Engineering Research Center,
Dept. of Computer Sciences, Purdue University, W. Lafayette IN 47907-2004
Internet:   uucp:   ...!{decwrl,gatech,ucbvax}!purdue!spaf

    [Mortifications from the Moderator, who tries to keep RISKS Readable
    by Hewing Headers.  In this case I should have left the entire sequence
    in, to add to the evidence described in the message.  Very clever.   PGN]

Intolerant Fault-Tolerance (RISKS-6.53)

Jerome H. Saltzer <Saltzer@ATHENA.MIT.EDU>
Sun, 3 Apr 88 14:10:38 EST
> From: mann (Tim Mann)  . . .
> This incident teaches two lessons about engineering a fault-tolerant system,
> neither of which should come as a surprise.   First, a fault-tolerant system
> must report the faults it tolerates ...


This lesson reported by Tim Mann bears underlining.  I would guess that the
single design mistake I have seen repeated most often in 25 years of observing
computer systems is that one: providing what appears to be fault tolerance, but
neglecting to provide a means of reporting when a fault has been encountered
and successfully masked.  As a result, many so-called fault-tolerant systems
actually run for much of their lifetime in a state where a single fault will
bring them down.  A redundant system that is thought to be operating well back
from the edge of a catastrophe cliff may actually be standing on the edge
without its users or operators being aware.

Examples are legion, even in the systems we use every day:

    -  backup tapes with write errors undiscovered till they are needed.
    -  packets mysteriously lost in the Ethernet or the gateway; the
       higher-level protocol successfully retries.
    -  the non-responding internet name server; the next one in the list
    -  mail links that are down more often than up; but up enough that
       the mail usually gets through.

A system that provides redundancy but omits any mechanism to call for
repair when the redundancy is invoked is more complex and expensive than
a non-redundant system, but it ISN'T really fault-tolerant.

A closely related problem occurs when a fault-tolerant system with properly
engineered fault reporting is operated in a mode where its calls for help get
ignored or given such low priority that they might as well not be there.  The
blame in this case isn't with the original engineers (unless they buried the
calls for help in the middle of a log full of uninteresting events), but the
RISK is the same.

Next time someone shows off a "fault-tolerant" system that seems to be able to
survive having a 45-caliber slug fired through one component, as part of the
demo ask to see the trouble report that the system generated in response to the
incident.  If there isn't one, take your business elsewhere.

                    Jerry Saltzer

``How Computers Get Your Goat''

Peter G. Neumann <>
Sat 2 Apr 88 10:46:01-PST
Anyone who has used a personal computer has been forced to wait while the
machine completed some task.  A University of Texas at Arlington researcher
has found that such waiting can produce anxiety and theorizes that such
anxiety reduces productivity.  The researcher, Jan L. Guynes, used
psychological tests to classify 86 volunteers as either Type A or Type B
personalities.  The volunteers were given 20 minutes to make editing
corrections on text in a personal computer, in which delays were programmed.
She found that a slow, unpredictable computer increased anxiety in both
groups equally, even though Type A personalities were generally more anxious
before undertaking the editing task, and that such added anxiety may affect

New York Times item, from the SF Chronicle, 30 March 1988, p. A3.

Old viruses

Mon, 4 Apr 88 17:31 EST
In a recent RISKS, Bill Kennedy mentions a program he saw on an IBM 360 back in
1974 which submitted multiple copies of itself.  This rang a bell; I remember
hearing talk of a similar program at Princeton.  Since I graduated in 1973, the
idea goes back at least that far.  No one claimed to have actually run it
themselves - it was always something they had heard about someone else doing.
But the possibility was certainly understood, and I recall discussions about
the consequences, and speculations about how many copies of itself the program
should submit for maximum effect.  (Anything more than an average of one was
certain to clog the system eventually; but you could modulate how long it would
take for the system to slowly grind to a halt.)

There was also discussion of counter-moves.  Given the way OS/360 and ASP were
structured, the best approach we could come up with was to remove the account
the program - just as in Bill Kennedy's story usually named "RABBIT" or
"RABBITS" - was running in.  Given the general insecurity of OS/360, however,
it wasn't hard to get different copies of RABBITS to run under many different
accounts.  Such a RABBITS program could be quite difficult and expensive to
kill - clearing out the queues on a batch-oriented system is not something to
be done lightly!

BTW, the great-granddaddy of all such programs wasn't a virus at all - it arose
innocently as a bug in some early version of OS/360.  The exact details are
lost in the mists of time, but they went something like this:  If your program
abend'ed (aborted), you got a post-mortem dump.  Some sort of job setting
requested that the dump be printed.  Often, you could quickly determine that
the dump was of no interest.  So you asked the operator to kill the print job.
Unfortunately, the "print dump on abend" switch stayed on:  Killing the print
job lead to a post-mortem dump....
                            -- Jerry

Re: Notifying users of security problems

Andy Goldstein <>
Mon, 4 Apr 88 15:28:53 PDT
> Date: 31 Mar 88 01:25:29 PST (Thursday)
> From: "hugh_davies.WGC1RX"@Xerox.COM
> Subject: Re: Notifying users of security problems
> In RISKS 6.50, Andy Goldstein ( states..
> "Sending out notice of the presence of a bug without a correction or
> workaround is of course even more irresponsible." ...
> When I first saw this I couldn't believe what I was reading. ...
> Please, Andy, tell me I've got it wrong!

Maybe you did misunderstand me; I should have been more precise in
the statement you quoted. I was referring specifically to security bugs.
That said, I stand by my statement. Let me try to explain...

When a piece of software is shipped containing a bug, knowledge of that
bug is contained in the software, in a manner of speaking. At the same
time, in most cases knowledge of the bug is not held by any person.
That is, the bug was created inadvertantly and unknowingly by the
author(s) of the software, and no one has discovered it yet.

A bug does its damage when it is somehow invoked, by use or misuse of a
certain feature, or by the unhappy confluence of certain conditions. By
and large, ordinary bugs are encountered by users innocently going about
their business. That is, no prior knowledge of the bug by the user is
involved in encountering the bug; knowledge of the bug by the system is
sufficient. Furthermore, the effect of the bug is in general to cause
system behavior which is undesirable to the user. Consequently,
knowledge of the bug will often permit the user to work around it or
defend against it. Since a virus spreads without knowledge of the user,
it too falls into this category. Sharing information about most types of
bugs, including the existence and nature of particular viruses, is
productive and worthwhile.

Now let us compare security bugs to ordinary bugs. I define a security
bug as one which permits a user to violate a system's security controls
in some significant way (e.g., allowing an ordinary user to become
superuser or whatever). Security bugs are by and large not encountered
by people innocently going about their business. They are usually found
by the adventurous by inspecting system sources, and are invoked only
through creative abuse of obscure system features. (I cannot argue this
point with logic, but many years of experience dealing with security
bugs tell me it is so.) Most system users (I mean users, not
administrators) do not care about security bugs. They do not stand in
the way of their getting their work done. The people who care about
security bugs are hackers (and of course the system managers trying to
fend them off). From the point of view of the hacker, a security bug is
an undocumented feature of the system that allows him to do what he
wants to do.

So we get to the critical distinction between security bugs and
others: Because invocation of a security bug requires a deliberate,
unusual action, a security bug is only harmful to an installation when
malicious users gain knowledge of the bug. The best analogy I can
think of is a lock manufacturer discovering that one of its locks can
be easily picked using a previously unknown technique. The challenge
we have with security bugs, therefore, is

(1) not shipping them to begin with
(2) fixing them as promptly as possible when they are discovered
(3) keeping knowledge out of the hands of the bad guys until they
    can be fixed.

Points (1) and (2) are of course mere matters of engineering,
manufacturing and distribution. Because we will never achieve
instantaneous development and distribution of bug fixes, (3) is the
kicker. I have heard many arguments that system managers should be
permitted to learn about security bugs, either from the manufacturer
or informally via the grapevine. With respect to the VAX/VMS user
community, I disagree with this conclusion for several reasons:

(1) The knowledge won't do them any good. We are long past the time
    when every computer installation had its wizard who knew (or
    thought he knew) how to fix every problem that might come up.

    [Digression: I'm sure half the university system managers have just
    hit the ceiling. Universities are unique in having available a large
    pool of cheap, highly talented labor. Among our engineering and
    commercial customers, technically skilled labor is expensive and
    hard to come by. Our working assumption is that the majority of
    our customer base does not, or would rather not have to, understand
    the internals of VMS to use it.]

(2) The news may do them harm. Would you, as DP manager of Bank of
    America, install a "security patch" that originated from, say,
    UC Berkeley?

(3) The knowledge may do them harm. Nowadays, any fairly well-off high
    school kid can buy himself a microvax and be a bona-fide system
    manager. There is no practical way to tell the good guys from the
    bad guys anymore. The larger the number of people know of the
    existence of a security problem, the more likely it is that a
    bad guy will gain the necessary knowledge to exploit it.

Consequently, DEC has taken the following approach to dealing with
security bugs in the future:

(1) When a security bug is discovered, engineering will develop a fix
    as rapidly as possible. The fix will be distributed to customers
    as rapidly as circumstances warrant. To the extent possible, the
    fix will be constructed so as to make it difficult to
    reverse-engineer the bug from the fix.

(2) Once the fix has been distributed, all customers will be notified
    of the existence of the problem and informed of the urgency of
    installing the fix. Thus we let the cat out of the bag (hopefully)
    only after users have been given the tools with which to skin it.

While this policy of secrecy does carry the possibility that a small number of
users may incur duplicated effort investigating a security bug, we feel this is
a worthwhile trade towards ensuring the safety of the majority of the customer
base. I also emphasize that this policy applies only to security bugs that have
no operational workaround.
                                        Andy Goldstein,  VMS Development

The "previous account" referred to in RISKS-6.51

Les Earnest <LES@SAIL.Stanford.EDU>
01 Apr 88 1620 PST
e-t-a-o-n-r-i Spy and the F.B.I.    

Reading a book got me into early trouble -- I had an F.B.I. record by age
twelve.  This bizarre incident caused a problem much later when I needed a
security clearance.  I learned that I could obtain one only by concealing my
sordid past.

A friend named Bob and I read the book "Secret and Urgent," by Fletcher Pratt
[Blue Ribbon Books; Garden City, NY; 1942] which was an early popular account
of codes and ciphers.  Pratt showed how to use letter frequencies to break
ciphers and reported that the most frequently occurring letters in typical
English text are e-t-a-o-n-r-i, in that order.  (The letter frequency order of
the story you are now reading is e-t-a-i-o-n-r.  The higher frequency of "i"
probably reflects the fact that _I_ use the first person singular a lot.)
Pratt's book also treated more advanced cryptographic schemes.

Bob and I decided that we needed to have a secure way to communicate with each
other, so we put together a rather elaborate jargon code based on the
principles described in the book.  I don't remember exactly why we thought we
needed it -- we spent much of our time outside of school together, so there was
ample time to talk privately.  Still, you never could tell when you might need
to send a secret message!

We made two copies of the code key (a description of how to encrypt and decrypt
our messages) in the form of a single typewritten sheet.  We each took a copy
and carried it on our persons at all times when we were wearing clothes.

I actually didn't wear clothes much.  I spent nearly all my time outside
school wearing just a baggy pair of maroon swimming trunks.  That wasn't
considered too weird in San Diego.

I had recently been given glasses to wear but generally kept them in a hard
case in the pocket of the trousers that I wore to school.  I figured that this
was a good place to hide my copy of the code key, so I carefully folded it to
one-eighth of its original size and stuck it at the bottom of the case, under
my glasses.

Every chance I got, I went body surfing at Old Mission Beach.  I usually went
by streetcar and, since I had to transfer Downtown, I wore clothes.
Unfortunately, while I was riding the trolley home from the beach one Saturday,
the case carrying my glasses slipped out of my pocket unnoticed.  I reported
the loss to my mother that night.  She chastised me and later called the
streetcar company.  They said that the glasses hadn't been turned in.

After a few weeks of waiting in vain for the glasses to turn up, we began
to lose hope.  My mother didn't rush getting replacement glasses in view
of the fact that I hadn't worn them much and they cost about $8, a large
sum at that time.  (To me, $8 represented 40 round trips to the beach by
streetcar, or 80 admission fees to the movies.)

Unknown to us, the case had been found by a patriotic citizen who opened
it, discovered the code key, recognized that it must belong to a
Japanese spy and turned it over to the F.B.I.  This was in 1943, just
after citizens of Japanese descent had been forced off their property and
taken away to concentration camps.  I remember hearing that a local grocer
was secretly a Colonel in the Japanese Army and had hidden his uniform in
the back of his store.  A lot of people actually believed these things.

About six weeks later, when I happened to be off on another escapade, my
mother was visited by a man who identified himself as an investigator from
the F.B.I.  (She was a school administrator, but happened to be at home
working on her Ph.D. dissertation.)  She noticed that there were two more
men waiting in a car outside.  The agent asked a number of questions about
me, including my occupation.  He reportedly was quite disappointed when he
learned that I was only 12 years old.

He eventually revealed why I was being investigated, showed my mother the
glasses and the code key and asked her if she knew where it came from.  She
didn't, of course.  She asked if we could get the glasses back and he agreed.

My mother told the investigator how glad she was to get them back, considering
that they cost $8.  He did a slow burn, then said "Lady, this case has cost the
government thousands of dollars.  It has been the top priority in our office
for the last six weeks.  We traced the glasses to your son from the
prescription by examining the files of nearly every optometrist in San Diego."
It apparently didn't occur to them that if I were a REAL Japanese spy, I might
have brought the glasses with me from headquarters.

The F.B.I. agent gave back the glasses but kept the code key "for our records."
They apparently were not fully convinced that they were dealing just with kids.

Since our communication scheme had been compromised, Bob and I devised a new
key.  I started carrying it in my wallet, which I thought was more secure.  I
don't remember ever exchanging any cryptographic messages.  I was always ready,

A few years later when I was in college, I got a summer job at the Naval
Electronics Lab, which required a security clearance.  One of the questions on
the application form was "Have you ever been investigated by the F.B.I."
Naturally, I checked "Yes."  The next question was, "If so, describe the
circumstances."  There was very little space on the form, so I answered simply
and honestly, "I was suspected of being a Japanese spy."

When I handed the form in to the security officer, he scanned it quickly,
looked me over slowly, then said, "Explain this" -- pointing at the F.B.I.
question.  I described what had happened.  He got very agitated, picked up my
form, tore it in pieces, and threw it in the waste basket.

He then got out a blank form and handed it to me, saying "Here, fill it out
again and don't mention that.  If you do, I'll make sure that you NEVER get a
security clearance."

I did as he directed and was shortly granted the clearance.  I never again
disclosed that incident on security clearance forms.

On another occasion much later, I learned by chance that putting certain
provocative information on a security clearance form can greatly speed up
the clearance process.  But that is another story.
                                                    Les Earnest

Just Another Unix Spoof -- ISO abandoned

Paul Cudney <>
Sat, 2 Apr 88 13:19:08 PST
Are you engaging in fault-encouragement behavior?  If so, here is
Just Another Unix Spoof (JAUS) to chew on.  /Paul

Path: sdcrdcf!ucla-cs!rutgers!bellcore!faline!thumper!kremvax!meese
Newsgroups: comp.protocols.tcp-ip,comp.protocols.iso
Subject: OSI abandoned!
Message-ID: <>
Date: 1 Apr 88 00:00:01 GMT
Organization: Soviet Sanctuary for Victims of American Persecution
Posted: Fri Apr  1 00:00:01 1988

    WASHINGTON -- In a simultaneous announcement that took the
computer industry by surprise, OSI leaders today said that they were
abandoning their effort to promote the OSI Protocol Suite in favor of
the existing US Department of Defense (DoD) ARPANET Protocol Suite. 

    The official reason cited for the decison was a new report from
the Office of Technology Assessment stating that the manpower required
to fully implement and test even the few OSI protocols that are now
defined would consume the entire output of American university computer
science programs for the rest of the century, and that printing and
distributing the necessary protocol specifications would consume the
entire American and Canadian paper supplies for the next five years. 

    However, one high-placed source speaking on condition of
anonymity said, ``The whole OSI thing was a practical joke one of the
guys cooked up a few years ago.  Nobody ever expected anybody to take it
seriously.  I mean, who would believe an organization supposedly
dedicated to tearing down barriers to free and open communications
between computers when it's run by a former director of the National
Security Agency? I guess computer people are a lot more gullible than we
thought.  We kept dropping hints, making the whole thing more and more
ridiculous. We hoped that people would eventually catch on, but it didn't
work.  Finally, our consciences got to us.''

    In related news, officials at the Mitre Corporation in Bedford,
Massachussetts reported that one of their employees, as yet publicly
unidentified, froze ``as solid as stone'' when he heard the announcement. 
Medical experts have as yet been unable to communicate with the victim
or get him to relax his facial muscles, which are reportedly locked into
what was described as an ``enormous grin''. 

    AP-NR-04-01-88 0001EST

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