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.:: The Blue Box And Ma Bell ::.

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Current issue : #25 | Release date : 1989-03-29 | Editor : Taran King
Phrack Inc. XXV IndexKnight Lightning & Taran King
25th Anniversary IndexTaran King & Knight Lightning
Bell Network Switching SystemsTaran King
SPAN: Space Physics Analysis NetworkIron Soldier
Unix Cracking TipsDark OverLord
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The Blue Box And Ma BellThe Noid
Hacking: What's Legal And What's NotHatchet Molly
Phrack World News XXV/Part 1Knight Lightning
Phrack World News XXV/Part 2Knight Lightning
Phrack World News XXV/Part 3Knight Lightning
Title : The Blue Box And Ma Bell
Author : The Noid
                                ==Phrack Inc.==

                     Volume Three, Issue 25, File 7 of 11

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      ^*^                                                             ^*^
      ^*^                  The Blue Box And Ma Bell                   ^*^
      ^*^                                                             ^*^
      ^*^                 Brought To You by The Noid                  ^*^
      ^*^                                                             ^*^
      ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^ ^*^

        "...The user placed the speaker over the telephone handset's
         transmitter and simply pressed the buttons that corresponded
         to the desired CCITT tones.  It was just that simple."

                          THE BLUE BOX AND MA BELL

Before the breakup of AT&T, Ma Bell was everyone's favorite enemy.  So it was
not surprising that so many people worked so hard and so successfully at
perfecting various means of making free and untraceable telephone calls.
Whether it was a BLACK BOX used by Joe and Jane College to call home, or a BLUE
BOX used by organized crime to lay off untraceable bets, the technology that
provided the finest telephone system in the world contained the seeds of its
own destruction.

The fact of the matter is that the Blue Box was so effective at making
untraceable calls that there is no estimate as to how many calls were made
or lost revenues of $100, $100-million, or $1-billion on the Blue Box.  Blue
Boxes were so effective at making free, untraceable calls that Ma Bell didn't
want anyone to know about them, and for many years denied their existence. They
even went as far as strongarming a major consumer-science magazine into killing
an article that had already been prepared on the Blue and Black boxes.
Furthermore, the police records of a major city contain a report concerning a
break-in at the residence of the author of that article.  The only item missing
following the break-in was the folder containing copies of one of the earliest
Blue-Box designs and a Bell-System booklet that described how subscriber
billing was done by the AMA machine -- a booklet that Ma Bell denied ever
existed.  Since the AMA (Automatic Message Accounting) machine was the means
whereby Ma Bell eventually tracked down both the Blue and Black Boxes, I'll
take time out to explain it.  Besides, knowing how the AMA machine works will
help you to better understand Blue and Black Box "phone phreaking."

Who Made The Call?
Back in the early days of the telephone, a customer's billing originated in a
mechanical counting device, which was usually called a "register" or a "meter."
Each subscriber's line was connected to a meter that was part of a wall of
meters.  The meter clicked off the message units, and once a month someone
simply wrote down the meter's reading, which was later interpolated into
message-unit billing for those subscriber's who were charged by the message
unit.  (Flat-rate subscriber's could make unlimited calls only within a
designated geographic area.  The meter clicked off message units for calls
outside that area.)  Because eventually there were too many meters to read
individually, and because more subscribers started questioning their monthly
bills, the local telephone companies turned to photography.  A photograph of a
large number of meters served as an incontestable record of their reading at a
given date and time, and was much easier to convert to customer billing by the
accounting department.

As you might imagine, even with photographs, billing was cumbersome and did not
reflect the latest technical developments.  A meter didn't provide any
indication of what the subscriber was doing with the telephone, nor did it
indicate how the average subscriber made calls or the efficiency of the
information service (how fast the operators could handle requests).  So the
meters were replaced by the AMA machine.  One machine handled up to 20,000
subscribers.  It produced a punched tape for a 24-hour period that showed,
among other things, the time a phone was picked up (went off-hook), the number
dialed, the time the called party answered, and the time the originating phone
was hung up (placed on-hook).

One other point, which will answer some questions that you're certain to think
of as we discuss the Black & Blue boxes:  Ma Bell did not want persons outside
their system to know about the AMA machine.  The reason:  Almost everyone
had complaints -- usually unjustified -- about their billing.  Had the public
been aware of the AMA machine they would have asked for a monthly list of their
telephone calls.  It wasn't that Ma Bell feared errors in billing; rather,
they were fearful of being buried under any avalanche of paperwork and customer
complaints.  Also, the public believed their telephone calls were personal and
untraceable, and Ma Bell didn't want to admit that they knew about the who,
when, and where of every call.  And so Ma Bell always insisted that billing was
based on a meter that simply "clicked" for each message unit; that there was no
record, other than for long-distance as to who called whom.  Long distance was
handled by, and the billing information was done by an operator, so there was a
written record Ma Bell could not deny.

The secrecy surrounding the AMA machine was so pervasive that local, state, and
even federal police were told that local calls made by criminals were
untraceable, and that people who made obscene telephone calls could not be
tracked down unless the person receiving the call could keep the caller on the
line for some 30 to 50 minutes so the connections could be physically traced by
technicians.  Imagine asking a woman or child to put up with almost an hour's
worth of the most horrendous obscenities in the hope someone could trace the
line.  Yet in areas where the AMA machine had replaced the meters, it would
have been a simple, though perhaps time-consuming task, to track down the
numbers called by any telephone during a 24 hour period.  But Ma Bell wanted
the AMA machine kept as secret as possible, and so many a criminal was not
caught, and many a woman was harassed by the obscene calls of a potential
rapist, because existence of the AMA machine was denied.

As a sidelight as to the secrecy surrounding the AMA machine, someone at Ma
Bell or the local operating company decided to put the squeeze on the author of
the article on Blue Boxes, and reported to the Treasury Department that he was,
in fact, manufacturing them for organized crime -- the going rate in the mid
1960's was supposedly $20,000 a box.  (Perhaps Ma Bell figured the author would
get the obvious message:  Forget about the Blue Box and the AMA machine or
you'll spend lots of time, and much money on lawyer's fees to get out of the
hassles it will cause.)  The author was suddenly visited at his place of
employment by a Treasury agent.

Fortunately, it took just a few minutes to convince the agent that the author
was really just that, and not a technical wizard working for the mob.  But one
conversation led to another, and the Treasury agent was astounded to learn
about the AMA machine.  (Wow! Can an author whose story is squelched spill his
guts.)  According to the Treasury agent, his department had been told that it
was impossible to get a record of local calls made by gangsters:  The Treasury
department had never been informed of the existence of automatic message
accounting.  Needless to say, the agent left with his own copy of the Bell
System publication about the AMA machine, and the author had an appointment
with the local Treasury-Bureau director to fill him in on the AMA machine.
That information eventually ended up with Senator Dodd, who was conducting a
congressional investigation into, among other things, telephone company
surveillance of subscriber lines -- which was a common practice for which there
was detailed instructions, Ma Bell's own switching equipment ("crossbar")

The Blue Box
The Blue Box permitted free telephone calls because it used Ma Bell's own
internal frequency-sensitive circuits.  When direct long-distance dialing was
introduced, the crossbar equipment knew a long-distance call was being dialed
by the three-digit area code.  The crossbar then converted the dial pulses to
the CCITT tone groups, shown in the attached table (at the end of this file),
that are used for international and trunkline signaling.  (Note that those do
not correspond to Touch-Tone frequencies.)  As you will see in that table, the
tone groups represent more than just numbers; among other things there are tone
groups identified as 2600 hertz, KP (prime), and ST (start) -- keep them in

When a subscriber dialed an area code and a telephone number on a rotary-dial
telephone, the crossbar automatically connected the subscriber's telephone to a
long-distance trunk, converted the dial pulses to CCITT tones, set up
electronic cross-country signaling equipment, and recorded the originating
number and the called number on the AMA machine.  The CCITT tones sent out on
the long-distance trunk lines activated special equipment that set up or
selected the routing and caused electro-mechanical equipment in the target city
to dial the called telephone.

Operator-assisted long-distance calls worked the same way.  The operator simply
logged into a long-distance trunk and pushed the appropriate buttons, which
generated the same tones as direct-dial equipment.  The button sequence was
2600 hertz, KP (which activated the long-distance equipment), then the complete
area code and telephone number.  At the target city, the connection was made to
the called number but ringing did not occur until the operator there pressed
the ST button.

The sequence of events of early Blue Boxes went like this:  The caller dialed
information in a distant city, which caused his AMA machine to record a free
call to information.  When the information operator answered, he pressed the
2600 hertz key on the Blue Box, which disconnected the operator and gave him
access to a long-distance trunk.  He then dialed KP and the desired number and
ended with an ST, which caused the target phone to ring.  For as long as the
conversation took place, the AMA machine indicated a free call to an
information operator.  The technique required a long-distance information
operator because the local operator, not being on a long distance trunk, was
accessed through local wire switching, not the CCITT tones.

Call Anywhere
Now imagine the possibilities.  Assume the Blue Box user was in Philadelphia.
He would call Chicago information, disconnect from the operator with a KP tone,
and then dial anywhere that was on direct-dial service:  Los Angeles, Dallas,
or anywhere in the world if the Blue Boxer could get the international codes.

The legend is often told of one Blue Boxer who, in the 1960's, lived in New
York and had a girl friend at a college near Boston. Now back in the 1960's,
making a telephone call to a college town on the weekend was even more
difficult than it is today to make a call from New York to Florida on a
reduced-rate holiday using one of the cut-rate long-distance carriers.  So our
Blue Boxer got on an international operator's circuit to Rome, Blue Boxed
through to a Hamburg operator, and asked Hamburg to patch through to Boston.
The Hamburg operator thought the call originated in Rome and inquired as to the
"operator's" good English, to which the Blue Boxer replied that he was an
expatriate hired to handle calls by American tourists back to their homeland.
Every weekend, while the Northeast was strangled by reduced-rate long-distance
calls, our Blue Boxer had no trouble sending his voice almost 7,000 miles for

...The user placed the speaker over the telephone handset's transmitter and
simply pressed the buttons that corresponded to the desired CCITT tones.  It
was just that simple.

Actually, it was even easier than it reads because Blue Boxers discovered they
did not need the operator.  If they dialed an active telephone located in
certain nearby, but different, area codes, they could Blue Box just as if they
had Blue Boxed through an information operator's circuit.  The subscriber whose
line was Blue Boxed simply found his phone was dead when it was picked up.  But
if the Blue Box conversation was short, the "dead" phone suddenly came to life
the next time it was picked up.  Using a list of "distant" numbers, a Blue
Boxer would never hassle anyone enough times to make them complain to the
telephone company.

The difference between Blue Boxing off of a subscriber rather than an
information operator was that the AMA tape indicated a real long-distance
telephone call perhaps costing 15 or 25 cents -- instead of a freebie.  Of
course that is the reason why when Ma Bell finally decided to go public with
"assisted" newspaper articles about the Blue Box users they had apprehended, it
was usually about some college kid or "phone phreak."  One never read of a
mobster being caught.  Greed and stupidity were the reasons why the kid's were

It was the transistor that led to Ma Bell going public with the Blue Box.  By
using transistors and RC phase-shift networks for the oscillators, a portable
Blue Box could be made inexpensively, and small enough to be used unobtrusively
from a public telephone.  The college crowd in many technical schools went
crazy with the portable Blue Box; they could call the folks back home, their
friends, or get a free network (the Alberta and Carolina connections -- which
could be a topic for a whole separate file) and never pay a dime to Ma Bell.

Unlike the mobsters who were willing to pay a small long-distance charge when
Blue Boxing, the kids wanted it, wanted it all free, and so they used the
information operator routing, and would often talk "free-of-charge" for hours
on end.

Ma Bell finally realized that Blue Boxing was costing them Big Bucks, and
decided a few articles on the criminal penalties might scare the Blue Boxers
enough to cease and desist.  But who did Ma Bell catch?  The college kids and
the greedies.  When Ma Bell decided to catch the Blue Boxers she simply
examined the AMA tapes for calls to an information operator that were
excessively long.  No one talked to an operator for 5, 10, 30 minutes, or
several hours.  Once a long call to an operator appeared several times on an
AMA tape, Ma Bell simply monitored the line and the Blue Boxer was caught.
(Now you should understand why I opened with an explanation of the AMA
machine.)  If the Blue Boxer worked from a telephone booth, Ma Bell simply
monitored the booth.  Ma Bell might not have known who originated the call, but
she did know who got the call and getting that party to spill their guts was no

The mob and a few Blue Box hobbyists (maybe even thousands) knew of the AMA
machine, and so they used a real telephone number for the KP skip.  Their AMA
tapes looked perfectly legitimate.  Even if Ma Bell had told the authorities
they could provide a list of direct-dialed calls made by local mobsters, the
AMA tapes would never show who was called through a Blue Box.  For example, if
a bookmaker in New York wanted to lay off some action in Chicago, he could make
a legitimate call to a phone in New Jersey and then Blue Box to Chicago.  His
AMA tape would show a call to New Jersey.  Nowhere would there be a record of
the call to Chicago.  Of course, automatic tone monitoring, computerized
billing, and ESS (Electronic Switching System) now makes that virtually
impossible, but that's the way it was.

You might wonder how Ma Bell discovered the tricks of Blue Boxers.  Simple,
they hired the perpetrators as consultants.  While the initial newspaper
articles detailed a potential jail penalties for apprehended blue boxers,
except for Ma Bell employees who assisted a blue boxer, it is almost impossible
to find an article on the resolution of the cases because most hobbyist blue
boxers got suspended sentences and/or probation if they assisted Ma Bell in
developing anti-blue box techniques.  It is asserted, although it can't be
easily proven, that cooperating ex-blue boxers were paid as consultants.  (If
you can't beat them, hire them to work for you.)

Should you get any ideas about Blue Boxing, keep in mind that modern switching
equipment has the capacity to recognize unauthorized tones.  It's the reason
why a local office can leave their subscriber Touch-Tone circuits active,
almost inviting you to use the Touch-Tone service.  A few days after you use an
unauthorized Touch-Tone service, the business office will call and inquire
whether you'd like to pay for the service or have it disconnected.  The very
same central-office equipment that knows you're using Touch-Tone frequencies
knows if your line is originating CCITT signals

The Black Box
The Black Box was primarily used by the college crowd to avoid charges when
frequent calls were made between two particular locations, say the college and
a student's home.  Unlike the somewhat complex circuitry of a Blue Box, a Black
Box was nothing more than a capacitor, a momentary switch, and a battery.

As you recall from our discussion of the Blue Box, a telephone circuit is
really established before the target phone ever rings, and the circuit is
capable of carrying an AC signal in either direction.  When the caller hears
the ringing in his or her handset, nothing is happening at the receiving end
because the ringing signal he hears is really a tone generator at his local
telephone office.  The target (called) telephone actually gets its 20
pulses-per-second ringing voltage when the person who dialed hears nothing in
the "dead" spaces between hearing the ringing tone.  When the called phone is
answered and taken off hook, the telephone completes a local-office DC loop
that is the signal to stop the ringing voltage.  About three seconds later the
DC loop results in a signal being sent all the way back to the caller's AMA
machine that the called telephone was answered.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                            CCITT NUMERICAL CODE
    Digit      Frequencies (Hz)

    1          700+900
    2          700+1100
    3          900+1100
    4          700+1300
    5          900+1300
    6          1100+1300
    7          700+1500
    8          900+1500
    9          1100+1500
    0          1300+1500
    Code 11    700+1700  for inward
    Code 12    900+1700  operators
    KP         1100+1700  Prime (Start of pulsing)
    KP2        1300+1700  Transit traffic
    ST         1500+1700  Start (End of pulsing)
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