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RISKS-LIST: RISKS-FORUM Digest Friday 1 April 1988 Volume 6 : Issue 53

FORUM ON RISKS TO THE PUBLIC IN COMPUTERS AND RELATED SYSTEMS ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

Contents: Virus attacks RISKS (Martin Minow) First International Conference on Secure Information Systems Wednesday's time trouble at SRC (and fault-tolerant systems) (Tim Mann via Jim Horning) Two old viruses (Bill Kennedy) Credit card limits (Richard Wiggins) Bankcard authorizations (John Pershing) Things that go POOF! (Vander-Vlis) Diving tables (Joel Kirsh, Keith Anderson) Re: Terminals and checking the facts (A.E. Mossberg)

The RISKS Forum is moderated. Contributions should be relevant, sound, in good taste, objective, coherent, concise, nonrepetitious. Diversity is welcome. Contributions to RISKS@CSL.SRI.COM, Requests to RISKS-Request@CSL.SRI.COM. For Vol i issue j, FTP SRI.COM, CD STRIPE:<RISKS>, GET RISKS-i.j. Volume summaries in (i, max j) = (1,46),(2,57),(3,92),(4,97),(5,85).

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Date: 1 Apr 88 00:00 From: minow%thundr.DEC@decwrl.dec.com (Martin Minow THUNDR::MINOW ML3-5/U26 223-9922) Subject: Virus attacks RISKS

Today, I'm afraid I must confess that one of my recent postings to Risks contained a Virus that Peter (no doubt inadvertently) distributed to the RISKS audience. The virus doesn't infect your programs or data files directly, but in a manner analogous to the "Christmas card" virus discussed here a few months ago, it causes increased network traffic.

As the virus establishes itself, you will note its affect by the increased amount of electronic mail you receive every day. For some of you, the increase is linear; but for others, I'm afraid you're on the early part of a exponential curve.

Although the virus was easy to create, I'm afraid that I don't know how to cure it. In fact, I believe I'm beginning to note its effects on my own system.

Humbly, Martin Minow

[I've been wondering where the dramatic increase was coming from. PGN]

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From: drm@reserch.uucp (Dennis Ritchie) Newsgroups: news.announce.conferences,news.announce.important Subject: First International Conference on Secure Information Systems Message-ID: <6.0225x10toda23@reserch.uucp> Date: 31 Mar 88 16:00:00 PST Expires: 1 May 88 00:00:00 GMT Sender: taylor@hplabsz.HPL.HP.COM Organization: AT&T Bell Labs, Unix Research

FOR IMMEDIATE RELEASE % FOR IMMEDIATE RELEASE [O.K. You are released. PGN]

The System Security Society of Southern Saskatchewan and the University of North Saskatchewan, Hoople campus announce the First International Conference on Secure Information Systems. This conference will feature a star studded panel of security and system experts from across the computing spectrum giving boring papers and comparing notes on security problems and possible solutions for existing and future operating systems ane networking environments.

Papers that will be given at the conference include:

Richard Brandow, MacMag magazine: Computer Viruses as a form of social terrorism

Dennis Ritchie, AT&T: Trojan Horses: Security Hole or Debugging Aid?

Richard M. Stallman, Free Software Foundation: Passwords are a Communist Plot, or Give Me Access to Your Computer, Dammit!

Chuq Von Rospach, Fictional Reality: A Secure USENET, an Exercise in Futility.

Greg Woods, NOAO: Benign Dictatorships in Anarchic Environments: A Case Study

Peter Honeyman, University of Michigan: Security Features in Honey-DanBer UUCP, or Why a Flat Name Space is Good.

John Mashey, MIPS Computers: RISC security risks on Usenet

Peter G. Neumann, SRI: The RISKS Of Risk Discussion, or Why This Conference Should be Classified.

William Joy, Sun Microsystems: Unix is Your Friend.

Donn Parker, SRI: Breaking Security for Fun and Profit: A Survey

Lauren Weinstein, The Stargate Project: Stargate Encryption; Turning Free Data into Revenue.

Mark Horton & Rick Adams, The UUNET project: Security Aspects of Pay for Play on USENET.

C. Edward Brown, National Security Agency: How to get USENET feeds when you don't exist, A Case Study.

Gordon Moffett, Amdahl Corp.: The USENET anarchist's cookbook; An alternative to the backbone cabal

John Quarterman, University of Texas: The USENIX social agenda and national security; A summary of Usenet discussions from Star Wars to Tar Wars.

Landon C. Noll & Ron Karro, Amdahl Corp.: Public Key Encryption in Smail3.1; How to send E-mail that the NSA can't read

A. I. Gavrilov, KGB, North American Information Bureau: Exporting American Military Information via Encoded USENET Signatures, Theory and Practice.

The Conference will be held March 2 through 4, 1989 on the campus of the University of North Saskatchewan in Hoople, Saskatchewan, Canada. Registration is $195 until December 1, 1989, $295 afterward. For more information please contact Professor Peter Schickele, Department of Computer Science, University of North Saskatchewan, Hoople, Saskatchewan, Canada 1Q5 UI9.

Note: This conference is a rescheduling of the conference originally scheduled for October, 1988 but cancelled after the United States Department of Commerce decided that the material was too sensitive to allow non-American citizens to read (including the material written by the Canadians on the committee). Because of this, the conference has been moved to Canada, which doesn't have a complete Freedom of Speech written into it's constitution, but has better things to do than worry about ways of circumventing civil rights. Americans having trouble getting their papers cleared for distribution at the conference should contact Professor Shickele about setting up a direct uucp link for the troff source.

[I received FIVE copies of this important announcement, so I must assume that some of you may have received multiple copies. However, for those of you who missed it, it seemed worth including here. I fixed the mispeling of Prof. Schickele's name. I'm sure he wouldn't mind. I also fixed the spelling out of Sask., for esthetic reasons. Otherwise this is as the message was received. PGN]

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Date: 1 Apr 1988 1440-PST (Friday) From: horning@src.dec.com (Jim Horning) Subject: Wednesday's time trouble at SRC (and fault-tolerant systems)

Forwarded Message:

Date: Fri, 1 Apr 88 14:12:02 PST [Not a joke.] From: mann (Tim Mann)

I've learned a bit more about what went wrong with our time service on Wednesday; here are the details for those who are interested.

Background: SRC's time service is based on three master clocks. Two of the clocks get their time signals from radio station WWV in Colorado, while the other gets its time signal from the GOES earth satellite. The master clocks are plugged into Fireflies, which periodically read them and broadcast the time on the net. Every Firefly on the net receives these broadcasts, and takes a fault-tolerant average to get the time to which it adjusts its local clock. This amounts to taking the median if all three time providers are heard from, the mean if two are heard, or the reported value if only one is heard. So we tolerate any single fault: if one time provider gives out bogus times, but the other two still work correctly, clients are not fooled. If two providers fail, clients can be fooled.

Around March 23, Mike Schroeder had trouble with his Firefly, which hosts one of the WWV clocks. Our hardware guys came up and fixed it, but left the console baud rate switch in the wrong position, so the time server couldn't read the clock. Now there were only two time servers, so clients took the mean and still got the right time. Unfortunately, the current time service implementation doesn't send a message to a human when this happens; it just logs the event in a place that's seldom looked at. So Mike's clock stayed down until yesterday afternoon, March 31.

Then on Wednesday afternoon (March 30), something really unusual happened. The WWV clock connected to my Firefly suddenly decided that it was July 8 (the 190th day of the year) instead of March 30 (the 90th day). About two hours later it switched back to March 30. But the incorrect readings had some bad consequences.

First, because there were now two faulty clocks, the client hosts could no longer cope. They took the mean of the two time providers that were reporting and started trying to advance their clocks to the 140th day of the year by running fast. The speedup was limited to 10% by a sanity check I put into the implementation, so it took quite a while before anyone noticed the incorrect time on his Firefly. (Again, when the 10% limit is hit, the current implementation just logs the event in an obscure place.)

The second bad consequence came from the way the current implementation initializes the time on bootup. Instead of averaging all the time servers, it just believes the first one it hears. So two people rebooted their machines on Wednesday afternoon, noticed that the time read "July 8", and phoned me. At that point I got to work picking up the pieces, and phoned the WWV receiver's manufacturer.

The next day one of the chief technical people from the time receiver company came out to try to figure out what had happened. In the end he ascribed it to a mysterious bug in the firmware release we were running, and gave me a new set of PROMs with an improved algorithm for rejecting erroneous data that shows up due to noise in the radio signal.

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 so they can be fixed, rather than masking them entirely. Second, a fault-tolerant system must tolerate faults in all phases of its operation---it is not okay if faults during normal operation are tolerated, but faults during initialization cause undetected errors. --Tim ------------------------------

Date: 29 Mar 88 19:41:16 CST (Tue) From: bill@ssbn.wlk.com (Bill Kennedy) Subject: Two old viruses

Someone asked for a virus dated prior to 1984. Back in 1974 I was working at a large firm with no fewer than three 360's lashed together and a bright young fellow wrote a program named "rabbit". When rabbit was submitted it had found a way of taking a copy of itself and tossing it back, twice, into the ASP input jobstream. One of ASP's famous qualities was how it got stingier and stingier about talking to its console when it began to get constipated. Needless to say, rabbit constipated it so it was harder to kill the longer it ran. The bright young fellow was (justifiably) discharged.

Also in response to the computer theft story I know a fellow who founded the first retail computer store in Texas. One day Dallas police came into his store (not in Dallas) and asked if he was familiar with a particular brand of Southwest Technical Products (*that* dates it!) video terminal. He said he was. They asked him if he knew how to operate the computer that came with the SWDP terminal, he was. Would he comne down to headquarters and look at some- thing? Sure... When he got the system to boot up he was unsure what the police wanted. They explained that they had just arrested a burglar and this computer was in his apartment. Neither the computer nor the terminal were "hot", the police had found sales receipts for each and the way they found the store was from a receipt for repair work done to the terminal. When the disk directory was played out for the detectives they nearly jumped for joy! The burglar had carefully and faithfully recorded each job, goods stolen, where fenced if fenced, and where stored if not fenced. Dallas and the surrounding cities cleared about eighty offenses just on a simple printout of the burglar's data files. The thief had also programmed it himself!

Bill Kennedy ...{rutgers,cbosgd,ihnp4!petro}!ssbn!bill or bill@ssbn.WLK.COM

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Date: Wed, 30 Mar 88 00:11:56 EST From: Richard_Wiggins@um.cc.umich.edu Subject: Credit card limits

A standard problem with credit card limits is that a firm can run your card to the limit with a hold, and you are then out of credit until the hold is resolved. (I, for one, would like definitive word on when holds are removed.)

Two cases in which holds for estimated amounts are used:

When you check into a hotel, they guess how much you are likely to spend based on the number of days and the room rate, plus a fudge factor for food or phone charges you might ring up. If you stay beyond your original plans, they continue to call in for additional authorizations, usually at the same estimated rate, regardless of how much you may have spent.

If you have an accident in a rental car, and you don't have the damage insurance from the rental agency, they may tie up your credit -- up to the limit, of course -- until you make a settlement. When a car I'd rented from National in Salt Lake City was struck by a deer a couple of years ago, they were quite sanguine when I called to report the problem. When I physically returned a few days later, they looked at the police estimate of $1100 and wanted to charge it to my credit card. I persuaded them that I was adequately insured, but they insisted on running through a blank charge slip and making me sign it. Since it was a long walk to the terminal I very reluctantly agreed. (My insurance paid, not my plastic.)

Now, one could imagine cases where a negligent or hostile clerk typos in the authorization process, and say, sends through a request for 10X the proper amount. You may have enough credit for that, but not for the next charge!

In light of all this, it seems prudent to carry more than one credit card, even if the same "brand".

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Date: 1 Apr 88 09:31:31 EST From: John Pershing <PERSHNG@ibm.com> Subject: Bankcard authorizations

The credit authorization process is essentially one big calculated risk. What typically happens is: the authorization request is submitted to the merchant's bank, which forwards it to the appropriate clearinghouse (one for each of the major cards). If the clearinghouse does not respond promptly (e.g., within 10 seconds), it counts as a tacit approval. We mustn't keep the customer waiting!

The clearinghouse's computer looks up the card number in its "negative file" of cards that are lost, stolen, or in arrears, and rejects the transaction if it finds an entry. Otherwise, it forwards the transaction to the bank that owns the account. If the owning bank does not respond promptly (e.g., within 5 seconds), it counts as a tacit approval. The clearninghouse then sends the answer ("yea" or "nay") back to the merchant's bank, and thence to the merchant.

Assuming that the computers at the banks and clearinghouses are all up 100% of the time, along with the communication networks, and that they are not so bogged down that they cannot respond in time, then the system always works. It's that simple! (...chuckle...)

Anybody want to venture a guess at the transaction load seen, e.g., by the MasterCard clearinghouse during the week before Christmas? Does anybody still wonder how a few bad authorizations manage to slip through the cracks? Can anybody think of a better way?

John A. Pershing Jr., IBM Research, Yorktown Heights

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Date: Thu, 31 Mar 88 08:35 EST From: Vander-Vlis@DOCKMASTER.ARPA Subject: Things that go POOF!

Having worked in a NYC bank for five years I must disagree with an earlier statement that a decomposed check is untraceable. The only way that the check could disappear without a trace is if it decomposed before the teller could process it. This is usually done at the end of the day. Each check must be marked with the banks cancellation stamp. This stamping is performed by a machine which, at the same time, takes a photograph of the check for bank records. When that check finally decomposes, there will be an accounting discrepancy between two financial institutions which (believe it or not) will be traced back to that photograph. This knowledge comes from the painful personal experience of sitting with a microfilm reader looking through all checks processed on a certain day in search of one bleepin' check.

This plot would more than likely be uncovered even if the check decomposed in the teller's drawer. If you ever watched your teller when making a deposit you know that he/she writes down the amount of cash as well as the amount of each check. If while proving their till for the day the teller can't come up with matching debits and credits they will cross-check their deposit slips with their checks and find the slip which doesn't have a check to go with it. Although they can not fault the depositor for the loss of the check, if this were to happen frequently, the bank would eventually become aware of it. Incidentally, this is an old scam. I'm surprised that it actually made the news at all.

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Date: Wed, 30 Mar 88 10:12 CST From: Joel Kirsh <KIRSH@NUACC.ACNS.NWU.Edu> Subject: diving tables

The user interface on the new diving computers is certainly critical, but most divers are still using the standard US Navy tables (which are orders of magnitude cheaper). These tables contain still another RISK, that of making unreasonable assumptions about the relevant characteristics of the user.

The allowable depths, times, and recommended decompression stops in the USN tables were determined from a population of physically fit, well-trained, and highly motivated subjects (ie USN divers). Even so, when followed exactly, the tables are expected to result in a finite percentage (on the order of 5%) of decompression injuries.

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Date: Wed, 30 Mar 88 11:08 EST From: Keith 'Dain Bramaged' Anderson <KANDERSON%HAMPVMS.BITNET@MITVMA.MIT.EDU> Subject: Diving Computers

I recently read a letter in this digest questioning the safety of the new diving computers ("The Edge" and "The Skinnydipper", by a company I forget the name of) and decided to add my 2 bits.

I have to explain a little about diving to explain these computers.

Air is made up of approximately 80% nitrogen. At sea level, our bodies are saturated with nitrogen. When a diver decends, the pressure exerted on his or her body increases one atmosphere for every 33 feet he decends (one at sea level, two 33 ft under, three at 66 ft under etc.). This increase forces more nitrogen into solution in the diver's body. If the diver absorbs too much nitrogen, it will bubble out of solution as he or she acends to lower pressure. Nitrogen bubbles in the bloodstream are bad (ahem). The Navy compiled tables using _men_ in the prime of health, of limits as to the amount of time a diver could stay at any depth (down to 150 ft) and then surface normally and not get the bends. These are the maximum No-decompression limits tables. These tables have a 5% failure rate. Another way to avoid the bends is to dive to a certain depth for a certain time, and then on acending, stop at 10 feet under for a a certain time to allow nitrogen to be outgassed, and then surfacing. These are called decompression dives, and also have a set of tables. What none of these tables allow for is the fact that if a diver dives to 90 feet for a while, and then acsends a little and spends the rest of his or her dive at 60 feet, the nitrogen absorbed at 90 feet will be outgassed at 60 ft until the 60 saturation point. What the new computers do is credit the diver with time spent at a lesser depth, and debit him or her for deeper depths. These computers also follow tables that are more conservative than the standard Navy tables, thus making for a safer dive.

The message that appears telleing a diver to acend more slowly is to prevent a different problem. The air coming out of a SCUBA tank arrives in the lungs at the same pressure as the surrounding water. If a diver fills his or her lungs with air at 90 psi (the pressure it is recieved at at 20ft), and then ascends to 10 ft under, the pressure decreases to 45 psi, so the air in the divers lungs tries to double its volume. The lungs have no nerves that tell the brain that they are being stretched too much, so they tear. This also is bad. The simple way to avoid this problem is to ascend slowly enough that the air has a chance to be expelled, and a new, lower pressure breath may be taken in. Divers have a bad habit of swimming to the surface too quickly ( the new optimum rate of acent is 20 feet per minute (!) this means it should take 5 minutes to acend from 100 feet down), and so the computers constantly warn divers to acend more slowly.

As for the question of bad human interfacing, a diver checks his or her air pressure frequently (wouldn't you ?), and the computers are designed to clamp onto the same hose that leads to the pressure guage, thus making it rather hard to miss.

Keith Anderson, Hampshire College, Kanderson@hampvms

P.S. you have just received the majority of the classwork in a SCUBA course.

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Date: Fri, 1 Apr 88 13:49:20 EDT From: a.e. mossberg <aem@miavax.miami.edu> Subject: Re: Terminals and checking the facts (RISKS-6.52) Organization: Univ of Miami Dept of Math and Computer Science - Hertz Lab

I'm afraid Jerry's flames are well deserved, before sending the letter I merely checked the TVI9220 and WYSE 85 manuals (the first, a 'vt220' compatible, the second, a 'vt200' compatible). They list a vt command for entering block mode (DECEDM) but only wyse and televideo specific commands for sending the contents of the screen. In the case of the televideo, the command is only in 9220 mode.

a.e.mossberg Bitnet: aem@miavax.miami.edu@cunyvm uucp: ...!uunet!miavax!aem SPAN: aem@mthvax.span (3.91)

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