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Newsletter Nov 2006

News update 2006-11: November 2006

1. Small error, big result
2. Nobody will ever…
3. Just pick it up and carry it
4. Newsletter information

1. Small error, big result

Guess what happens when you put the wrong data in? Surprise,
surprise, you get the wrong answer out at the other end. This has
just happened to HBOS, where the accumulated wrong answers are
worth £17m.,,1958434,00.html

Apparently there’s been an error in the unit pricing data for four
years. It all started about four years ago, when a decimal point
was put in the wrong place. The errors have mounted up over time.
The problem was noticed around a year ago, and since then Clerical
Medical (the arm of HBOS where this happened) have gone back
through all their policy records to work out exactly which policies
have been affected and by how much.

There are a couple of interesting issues here.

The first one is, of course, the way the mistake happened to start
with. The press stories imply that it was a simple data input
error: somebody typed the wrong number, 23.4 instead of 2.34 or
something like that. It’s easy to do. I know I’ve mistyped things
in the past, and I’m sure you have too. The question is, how can
data input errors be prevented?

Well, first off, you try to avoid manual data input. Most data
comes from a computer anyway, and you try to set up a direct feed
rather than rely on somebody reading numbers from a screen or
printout and typing them in. If it turns out that a direct feed is
impossible, maybe you try copying and pasting: there are plenty of
risks there, but they are different to those of manual input.

You also want to have some sort of data validation on the inputs:
maybe a range outside which entries are queried, or a maximum
difference between the new value and the old value, or between it
and other, related values. It’s often difficult to set this sort of
thing up so that there are no false alarms and all errors are
caught, but these data validation checks are nevertheless useful.

Another option is to have some higher level checks built in. Maybe
all manual data inputs have to be made twice, by different people.
This is time-consuming and a bore, so it may be overkill in many
cases. Or you can set up some check totals: make sure that the
entries that have just been input add up to the same as the total
on the sheet from which you are copying them. This can mean
inputting data you don’t actually need, because it’s included in
the total, but it’s sometimes worth it.

The second interesting issue is connected with overall
reasonableness checks. It sounds as if the error was small at the
beginning, so wasn’t noticed. Then, as it grew larger, it still
wasn’t noticed. This is pure speculation on my part, but people
often do reasonableness checks in terms of the difference from one
time period to the next. And in this case, as no new error was
introduced, everything would be consistent so nothing wrong would
be noticed.

A really important lesson to learn is that consistency with the
prior period, or previous version, doesn’t necessarily mean that
there’s no error. It just means that there is no new error, or that
any new error is insignificant. And errors don’t always stay

More generally, relying on the results being consistent with your
expectations, or being reasonable in the light of your experience,
can be risky if your expectations or experience are based on the
use of the system that you are assessing. If you’ve been using a
program for some time, you have probably built up some expectations
about how the results are likely to vary with the inputs, and
you’ll probably have some good explanations of why things work in
the way they do. However, this can be risky; we tend to be very
good at post hoc rationalisation. If you rely on overall
reasonableness checks, or on consistency with experience, you need
to be sure that your checks are genuinely independent, rather than
being based on your experience of the system you are trying to

2. Nobody will ever…

The space shuttle can’t cope if it’s off the ground over 31st
December/1st January. Or, at least, its software can’t cope. The
software is about 30 years old, and doesn’t have any way of moving
from day 365 of the year back to day 1. So on 1 January 2007, for
example, it will think it is day 366 of 2006. Although they’ve done
simulations of flights lasting over the year end, and have
encountered no problems, NASA isn’t keen to try it in earnest.
There are distinct echoes of Y2k here. Nobody really knows if
anything will go wrong, but they don’t want to risk it.

It just shows that the “nobody will ever want to do X” design
principle is one to be avoided. Also, of course, that software can
stay in service much longer than you expect.

And, of course, nobody would ever hack into an ATM using an MP3
player. Except that Maxwell Parsons did. He targeted free-standing
ATMs (ie, not built in to walls) in bars and bingo halls. They were
connected to the bank using an ordinary telephone line, and as they
were free-standing he could physically get at it. He used the MP3
player to record the data going down the line,and then decoded it
on a laptop and used it to counterfeit credit cards. Apparently the
banking industry have now plugged the loophole.,,29389-2453590,00.html

3. Just pick it up and carry it

We tend to think of data theft as being primarily a network
problem: nasty people hack into a computer somewhere, and syphon
off the data; or they persuade nice people to visit a nasty
website, and enter confidential information. Physical theft is
pretty common, though. Laptops can and do hold vast amounts of
data, and are very easy to pick up and carry. Just this month, in
the UK, three laptops containing payroll details of 15,000
Metropolitan Police officers were stolen from LogicaCMG, and a
laptop containing customer information was stolen from an employee
of the Nationwide building society.

Often the data theft is probably accidental–it’s the laptop that’s
the real target, rather than the data on it–but that doesn’t
really make the data any more secure. In some cases it’s against
company policy to hold confidential data on a laptop. You’d think
that this should be the general rule, with very few exceptions.
Yes, it may be convenient to be able to work at home, or while
you’re travelling, but do the benefits outweigh the risk?

Physical security isn’t an issue only where laptops are concerned.
Earlier this month thieves stole a number of router cards from a
London data centre, resulting in serious service disruptions. A
couple of weeks earlier thieves got into a different data centre,
and drove off with a van full of equipment.,1000000189,39284520,00.htm

If they could get in and walk (or drive) off with equipment, what’s
to stop them walking off with whole disk drives or servers?

4. Newsletter information

This is a monthly newsletter on risk management in financial services,
operational risk and user-developed software from Louise Pryor
( Copyright (c) Louise Pryor 2006. All
rights reserved. You may distribute it in whole or in part as long as
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