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 64

Monday 18 April 1988


o Risks of reprogramming keyboards
John Coughlin
o Fear of flying?
Daniel B Dobkin
o "Flight international" magazine about civil avionics
L. Strigini
o Another STARK investigation; faulty simulation implicated?
Jon Jacky
o Re: Ethnics and UCB
Bob Ayers
o Re: More evidence for an old risk — Enigma
Henry Spencer
o Re: DEC's recent security patch
Darren Griffiths
o Info on RISKS (comp.risks)

Risks of reprogramming keyboards

18 Apr 88 11:21:00 EDT
   Last week a user of one of our mainframe systems called me with a couple of
problems.  She had logged on to a printer terminal to produce a hardcopy of
important electronic mail messages.  After a couple of messages had printed,
garbage characters appeared on her terminal.  "Sounds like a problem with flow
control, this shouldn't be difficult to set right," I assured her.  She then
explained that when she later logged on to her CRT, the messages which she has
tried to print had been deleted from her email folder.  She insisted that she
had not typed the DELETE command herself. It was not very likely that some
malicious individual had selectively deleted the exact same range of messages
which had been displaying, so I was at a loss to explain their disappearance.
I was able to restore most of her email from backup tapes, after which I
proceeded to investigate her terminal problem.

   The mainframe she uses recognizes several different flow control algorithms
for asynchronous terminals, although DC1/DC3 is the only one honoured under
most conditions.  The user's hardcopy terminal had a microswitch set to use
ACK/ETX protocol, so I switched it to use DC1/DC3.  Before I had changed the
position of the microswitch the terminal would have been sending ACKs to the
mainframe, which would have passed them through to its typeahead buffer. Now, I
knew that this user's logon was one of a large group which operate within a
more-or-less canned environment.  All users within this group share a set of
key bindings defined using a program called the Input Manipulation Processor
(which is aptly known as IMP for short).  I discovered (to my horror) that one
such IMP key binding mapped ^F (the ACK character) to the string 'DELETE'
followed by a carriage return. So what must have been happening is this:

   1. The  unfortunate  user enters the mail program and directs  it  to
      display a range of messages (this also has the effect of selecting
      them for further operations).

   2. At  some point the terminal's buffer is getting full,  so it  ACKs
      the mainframe to instruct it to stop sending for a while. This ACK
      is translated to  a  DELETE  command,  which  is  placed  into the
      typeahead buffer for processing. Meanwhile, the mainframe keeps on
      blasting data at the terminal.

   3. The terminal's buffer is overrun,  so many characters are lost and
      garbage is spewed  upon  the  paper.  Hidden  at  the  end of this
      garbled  mess is an illegible message informing the user that some
      of her email messages have been deleted, as "requested".

   This experience brings to light three RISKS.  First, it is risky to set up
naive users to have automagical key bindings of which they are unaware.  Such
users are not likely to understand the possible ramifications under unusual
circumstances (or even normal operation).  Second, destructive commands, such
as deletions not requiring confirmation, should not be bound to 'magic'
keystrokes such as PF keys, escape sequences and so on, for *any* user. This
just makes it too easy to cause irreversible damage with a typing mistake.
Finally, system-defined keystrokes are not a good place to start redefining
one's keyboard.  Communications control characters (DC1, DC3, ACK, etc.) and
interrupt keys (BREAK/ATTN, ^C or ^Y on many systems, etc.) should probably be
left alone.

fear of flying?

Daniel B Dobkin <dbd@vx2.GBA.NYU.EDU>
Mon, 18 Apr 88 11:52:56 EST
The following is excerpted, without permission, from the May 1988 issue
of "Private Pilot" magazine:

  The problem of maintenance is sometimes aggravated by the occasional
  mechanic or technician who doesn't believe that any pilot can report symptoms
  accurately and therefore ignores whatever the pilot says.  I encountered
  this with an instrument years ago, when the technician flatly refused to
  believe what the instrument was doing.  Instead, he just assumed it was
  something else for which he performed some unnecessary repair and returned
  the instrument with the original defect still preseent.  This resulted in
  four separate attempts to correct the malfunction.  Admittedly, some pilots
  are not precise in their reports, an this naturally leads to some degree of
  skepticism on the mechanic's part, but in most cases a few questions and a
  little discussion will clarify the uncertainties.

  The most important way to avoid this trap is to tell the mechanic exactly
  what you observed, @i{without interpretation}.  There's plenty of chance to
  compare your conclusions with his after he knows what symptoms there are.
  If you tell a person your conclusion in advance, it can bias and channel his
  thinking into a particular problem, which may be incorrect and delay the
  ultimate resolution.

This was passed on to me by a friend who reports similar failures of
communication between the systems group and the data center operators; he
has been awakened at 4:30 too many times by operators who report their
analyses of the problem, rather than the clear, concise descriptions he
needs.  Of course, at that hour he is more likely to follow the operator's
erroneous logic at first, thereby prolonging his discomfort; during the day,
SOP is to reject the operator's conclusions and attempt to coax him into
describing the problem.

"Flight international" magazine about civil avionics

Mon, 18 Apr 88 18:00 SET
The April 16 issue of "Flight international" features a 4-page article
"Software versus the black box", about current trends in civil avionics
(software-based fly-by-wire, etc.).

There is much about the A-320 (partially critical: maintainance still
difficult, for instance), some discussion of the pros and cons of
innovation: e.g. some think multifunctional displays to be difficult to deal
with in emergencies, more software in fewer black boxes should simplify
maintenance (of the boxes) but increase complexity, etc.

On software diversity: comments by several people to the effect
that it is possible to build "a lot more" than in the past in software,
but "Software risk cannot be quantified in meaningful terms" (attributed
to Brian Tucker, GEC Avionics): hence the need to protect oneself
somehow. On the other hand, one of the managers in the Airbus
program is quoted as saying "Common mode failures are not possible"
("confidently" says the magazine. !!!).

Other topics: the huge costs of avionics maintainance and ways to deal
with it (redundancy, self-reconfiguration to keep aircraft
flying, automated diagnosis to help repair, expert systems - of course);
proposals to "increase" airport capacity by better precision
in arrival times of flights (computers making sure an aircraft fits
exactly in the time slot reserved for it).

It may make interesting reading for RISKS readers, in particular because it
is written for non-computer specialists with an interest in computer risks.
Final quote: "What the airlines want .. is avionics designed for
certification and operating profits - a discriminate use of new technology".
Worth considering in relation to the recent discussions about responsibility.

Lorenzo Strigini

Another STARK investigation; faulty simulation implicated?

Jon Jacky <>
Mon, 18 Apr 88 16:52:15 PDT
From IEEE INSTITUTE 12(5) May 1988 p. 1:


Apparently unsatisfied by US Navy reports, the Congress is investigating
the combat capability of FFG-7 class frigates - those similar to the USS
STARK.  The STARK failed to deter two Exocet missiles, fired by an Iraqi
fighter jet in the Persian Gulf May 17, 1987, that resulted in 37 deaths
and more than $100 million in damage to the ship. ...
The investigation was requested in November 1987 by Rep. Barbara Boxer
(D-Calif), a member of the House Armed Serviced Committee and its 
investigations subcommittee. ... (Much discussion of weapons systems 
under investigation...) 

(Former STARK captain Glenn R.) Brindel told THE INSTITUTE that the Navy
combat systems doctrine manual said both the SPS-55 surface search radar
and the SPS-49 air search radar should detect Exocets fired from aircraft
at ranges over 15 miles.  "That is just a bunch of baloney," he added.
It gave the persons in the ship's combat information center a false sense
of security, he said.  The Navy's reported to have found that the 
capability listed in the manuals, put out by the commanders of the Atlantic
or Pacific surace fleets to address the capabilities of each ship class 
against specific missiles, was "significantly overoptimistic."  Boxer's aide
says the GAO is investgating how these capabilities are derived.  Brindel
says much of the data for these manuals is based on simulations. ...

The NAVY TIMES, quoting an unnamed source, reported on March 28 that (in a 
live test) Exocets (obtained for testing) "popped up" and were detected 
briefly by the frigate's radar while they were at high altitude.  But
after the missiles swooped low over the wave tops and began homing in on
the ships, the frigate was unable to detect them. (This test occured before
the STARK attack.  Discussion followed of whether the fleet was informed 
of the test results).

- Jonathan Jacky, University of Washington

Re: Ethnics and UCB (RISKS-6.63)

Bob Ayers <>
Mon, 18 Apr 88 09:52:03 PDT
    This is hearsay, so take it with a grain of salt, but I was told by a
    friend that he started filling the ethnicity slot on forms at UCB with
    "prussian".  This apparently did not default to "white".

Of course not. It defaulted to blue.

Re: More evidence for an old risk — Enigma

Mon, 18 Apr 88 06:02:29 EDT
Those interested in this should probably also read Patrick Beesly's book
"Very Special Intelligence" (1977).  It's the story from the user end:
an account of the British Admiralty's Operational Intelligence Centre,
which was charged with putting intelligence information together into a
useful form for naval operations.  In particular, it was effectively the
nerve center for the Battle of the Atlantic.  It had a dedicated teletype
link to the Bletchley Park cryptanalysts.  Apart from the inherent interest
of the user's-eye view, most of what OIC did is declassified, unlike a lot
of the detailed doings of the cryptanalysts.

Concerning "probable word" attacks on ciphers, Beesly observes that a
possible factor in the success of the cryptanalysts was that situation
reports from weather aircraft were often sent to shore in relatively low-
security ciphers and then rebroadcast verbatim in the high-security naval
ciphers.  Later in the war the Admiralty had to make a substantial effort to
discourage the RAF from shooting down those aircraft, without revealing why!

He also sheds some light on the question of why the cryptanalysis was not
discovered.  The Germans did persistently suspect either treachery or
cryptanalysis.  Against the former they took increasingly elaborate
precautions.  The possibility of the latter was investigated not once but
several times.  Unfortunately, the investigation was always run by the
signals people themselves, and the conclusion invariably was that they
were not at fault, i.e. the ciphers were unbreakable.

The situation wasn't as obvious as people might think, also.  Encryption
keys changed daily, and the cryptanalysts were often two or three days
behind in finding the new ones.  Cryptanalysis was often incomplete. And
the Germans used increasingly-elaborate map codes for geographic locations,
meaning that a message was often hard to interpret even if cryptanalysis
was complete.  The result was that OIC had to work hard to put things
together with other intelligence reports (e.g. direction-finding and actual
sightings), and errors did creep in.  These errors showed, and made it
harder to see that cryptanalysis was involved.

(For the same reasons, Beesly has a low opinion of some of the popular
books on wartime cryptanalysis.  Some of them make it sound like the Allies
knew everything the Germans were doing, and if any Allied ships were lost,
it was because of Machiavellian scheming by Allied commanders.  Beesly
makes it clear that it just wasn't that simple.)

A contributing factor may have been something that Beesly mentions as a
problem with OIC:  because there were few people qualified, cleared, and
available to do the work, and the workload was heavy, and the atmosphere was
one of constant crisis, nobody ever really got a chance to stand back for a
while and think about the deeper implications of events.  Nobody was charged
with looking for things like signs of hostile cryptanalysis.  Only a lucky
hunch by a senior man would reveal such a situation.  The British got lucky:
early in 1943 the head of OIC, Rodger Winn, noted for his lucky hunches,
concluded (correctly) that the *Germans* were reading the *Allied* naval
ciphers, and made enough of a stink to get things done about it.  Evidently
none of his German counterparts ever had a similar stroke of insight.

Beesly's account also has something to say about the perils of becoming
obviously dependent on one information source.  OIC had little cryptanalytic
intelligence for most of 1942, because the Germans had changed ciphers
and the cryptanalysts took a long time to solve the new one.  The OIC
people decided to try to continue detailed tracking of all U-boats,
recognizing that there would be many more errors.  Many people thought that
this was silly and wasn't going to work.  In fact it worked moderately
well, and the skeptics were proved wrong, but only because Winn and others
insisted that this "obviously" ridiculous scheme was worth trying.

Henry Spencer @ U of Toronto Zoology   {ihnp4,decvax,uunet!mnetor}!utzoo!henry

Re: DEC's recent security patch

Darren Griffiths <dagg@Csa1.LBL.Gov>
Mon, 18 Apr 88 16:42:34 PDT
This is a follow up to my recent article.  In the article I talked about
problems with the latest security patch from DEC.  In summary the problems
were caused by a fix to the TTDRIVER that helped stop trojan horse programs.
The fix, in some situations also broke the VAX Workstation Software, stopping
uses from autologging into a window.  Other things that were broken include
programs like PHOTO that use psuedo-terminal drivers to act as session loggers.

It seems that some of the programs that use psuedo-terminal drivers will
have to be modified before they will be able to work again.  This is
unfortunate, but it is necessary to provide extra security on VMS systems.
I believe DEC is planning to send out a letter describing these problems.

The problems with workstation software being broken can easily be fixed.
Patches to WTDRIVER.EXE and UISBG.EXE were distributed with the security
update, when these patches are installed the workstation software will work
as advertised with a secure TTDRIVER.  The problem is that the procedure
that checks to see if the workstation has VWS installed has a bug in it, and
it sometimes reports that the workstation software isn't installed when it
is.  If this happens the good software won't be installed and things will be
broken.  The easy fix is to look in the install save set for four images:

   UISBG031.EXE;8      UISBG032.EXE;1       

Take the ones appropiate for your versions and place them in
SYS$SYSTEM:WTDRIVER.EXE and SYS$SYSTEM:UISBG.EXE, that should fix things up.

I do encourage everyone to install these security fixes.  They ARE important
and they do help protect your system.  DEC has been getting a lot of flames
regarding their policy towards security issues, I am not sure that all of these
flames are deserved.  DEC engineers have spent a lot of time helping find this
problem, and they have always been eager to look for problems and suggest
solutions.  Before we go and flame DEC, why not spend some time flaming the
people (pond-scum?) who are trying to break into systems and wasting valuable
time and resources.  It is people like this who are the true cause of the
problem, not companies like DEC. 

I have heard comments recently that suggest it is the computer manager's
responsibility to maintain a secure environment for the users.  While this is
true it can only be taken so far.  It is reasonable to ask home owners to lock
their front door when they leave, it is not reasonable to ask them to hire
security guards and install a $10,000 alarm system.  At the same time it is
reasonable to ask computer managers to have a secure environment, it is not
reasonable to ask them to spend a good part of their life tracking down idiots
who persist on penetrating systems, particularly when the majority of these
systems have no useful or interesting information online.

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