1. Telephone Network Security and the Capn Crunch whistle in the 1960s and early 1970s

2. 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.

3. The Telephone Network of the 1960s 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.

4. Hierarchical Network

5. 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.

6. 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.

7. Signaling Cont. In order to reduce the probability that a human voice will mimic switch signals, special tone pairs were used.

8. 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.

9. Push Button Local Loop Signaling

10. 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)

11. Interoffice Signaling A different signaling protocol is needed to prevent a user from sending signals to switches downstream.

12. Interoffice Signaling

13. 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.

14. A Blue Box Device

15. 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-STKP-095-ST KP-252-0011-ST Ring

16. 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)

17. 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.

18. 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.

19. What about the Capn!?!