Telephone Network Security
and the “Cap’n Crunch” whistle
in the 1960’s and early 1970’s
Overview
•
The telephone network topology.
•
Telephone switch signaling protocols.
•
What is Phone Phreaking?
•
Hacking the telephone network of the 1960s
and 1970s.
•
What was done to fix the problem.
The Telephone Network of the
1960’s and early 1970s
•
Primary function of a telephone network is
to connect telephones together.
•
Not feasible to connect every user to every
other user directly.
•
A network is needed.
•
Hierarchical Network.
Hierarchical Network
Hierarchical Network
•
Lowest level
–
end users connected to local
exchange.
•
Next level up
–
local exchanges connected
to the primary trunk exchanges.
•
Next level up
–
the primary trunk exchanges
connected to the secondary trunk
exchanges.
•
Can extend to as many levels as needed.
Signaling
•
Signaling is the means by which routing
information is sent to switches.
•
Two main types of signaling.
–
Local
-
loop signaling
–
Interoffice signaling
•
Signals were sent on the same line that was
used to transmit voice.
Signaling Cont.
•
In order to reduce the probability that a
human voice will mimic switch signals,
special tone pairs were used.
Local
-
Loop Signaling
•
User picks up a telephone and “dials” a
number.
•
Two types
–
Rotary
–
Push Button
•
The switch at the local exchange routes the
number.
Push Button Local Loop
Signaling
Phone Phreaking
Phreaking
–
1. The art and science of cracking
the phone network (so as, for example, to
make free long
-
distance calls.)
2. By extension, security
-
cracking in any
other context (especially, but not
exclusively, on communication networks)
Interoffice Signaling
•
A different signaling protocol is needed to
prevent a user from sending signals to
switches downstream.
Interoffice Signaling
The Blue Box
•
Codes for interoffice signaling were
published in a Bell Labs journal article.
•
A box with 7 buttons could be built to route
a call anywhere in the world!
•
The first device confiscated by the phone
company was blue.
•
Steve Wozniak was in the Blue Box
business.
A Blue Box Device
How to make a free phone call
Phone
Local Exch.
Account.
System
Primary Exch.
Secondary Exch.
Primary Exch.
Local Exch.
Phone
1(800)555
-
5555
KP
-
187
-
ST
KP
-
07
-
ST
KP
-
095
-
ST
KP
-
252
-
0011
-
ST
Ring
Was the telephone system a
secure network?
•
The routing signals are sent over the same
lines that carry voice signals (in
-
band).
•
Cost must have been a factor.
•
Not only free calls
–
Bouncing calls between switches (untraceable)
–
Flooding the network (Denial of service)
How was it fixed?
•
By 1976 virtually all interoffice trunks were
converted to a new type of signaling
–
Common Channel Interoffice Signaling
•
Interoffice signals sent over separate lines.
Benefits of CCIS
•
Reduces call time set up.
•
Eliminates false customer simulated in
-
band
signaling.
•
Send data out of band, parallel to the voice
circuit.
What about the Cap’n!?!
Enter the password to open this PDF file:
File name:
-
File size:
-
Title:
-
Author:
-
Subject:
-
Keywords:
-
Creation Date:
-
Modification Date:
-
Creator:
-
PDF Producer:
-
PDF Version:
-
Page Count:
-
Preparing document for printing…
0%
Comments 0
Log in to post a comment