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Friday, August 10, 2001 |
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>http://news.bbc.co.uk/hi/english/sci/tech/newsid_1481000/1481783.stm
Thursday, 9 August, 2001, 13:44 GMT 14:44 UK
Bad start for Internet bench: The teenagers took advantage of the free service
Two teenagers discovered the world's first Internet bench could be used to
make free international telephone calls. The cyber-seat, which is based in
a public park in Suffolk, UK, went online on Monday. Neil Woodman and Dan
Sanderson, both 17, took a normal telephone handset along to the bench,
which was created by Microsoft's MSN service in partnership with the local
council. The pair cheekily phoned St Edmondsbury Council to warn them of
the problem and then tried to call Microsoft boss, Bill Gates. [Richard Jay Solomon via risks-digest Volume 21, Issue 59]
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> The cause was a hoax SMS spreading in the network of one of the GSM
> operators stating that it is possible to make free calls using this
> number.
Slowly the details of the case have emerged and - not surprisingly -
revealed another common risk - a risk of not assessing the effects of a
software change, even if it is fixing a simple bug.
There really _was_ the possibility to make free calls. Let zzz be the
emergency number. If you called zzz, the call was properly routed. If you
called zzzyyyyyy, a software bug caused zzz to be stripped and the call was
routed to yyyyyy instead. Charging software looks at the beginning of the
number and have seen an emergency number, so such call was not billed.
Then the operator fixed the bug and the fix was analogous to plain old
telephone - ignore remaining digits. Suddenly, all of such calls ended at
the firefighters.
So we are back to software development basics: specify handling of an
invalid input, test the handling and think before you make a fix public. The
fix was good enough for the billing department, but caused massive problems
somewhere else. [Stanislav Meduna via risks-digest Volume 21, Issue 59]
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Maximillian Dornseif, 2002.
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