Security apparatus and method for computers connected to telephone circuits

• US 4,905,281 A
• Filed: 05/04/1988
• Issued: 02/27/1990
• Est. Priority Date: 05/04/1988
• Status: Expired due to Fees

• Current Assignee: Halliburton Company
• Original Assignee: Halliburton Company
• Inventors: Penn, Jack C., Surjaatmadja, Jim B.
• Primary Examiner(s): Buczinski, Stephen C.
• Assistant Examiner(s): Gregory, Bernarr Earl
• Application Number:
  US07/190,284
• Time in Patent Office: 664 Days
• Field of Search: 380/23, 380/25, 380/49, 380/50, 380/59, 364/200, 364/900, 455/26.1, 379/90, 379/93, 379/195-199, 340/825.31, 340/825.34
• US Class Current: 726/23
• CPC Class Codes: G06F 21/313 using a call-back technique via a telephone network

Abstract

A security apparatus for interfacing a computer system with a telephone circuit includes a modem and a controller interfacing between the telephone circuit and a modem of the computer system. The first-mentioned modem and the controller operate to answer incoming calls in a manner to disguise that the telephone circuit is connected to a computer system, thereby masking or hiding the computer system from unauthorized users such as "hackers."

Claims

1. A system for connecting a computer with an incoming call over a telephone circuit, said system comprising:

a first modem, including means for connecting to the telephone circuit;

a second modem, including means for connecting to the computer; and

controller means, connected to said first modem and said second modem, for controlling said second modem in response to a validated incoming call being received through said first modem so that said computer is communicated through both said second modem and said first modem to said telephone circuit to receive the validated incoming call.

2. A system as defined in claim 1, wherein said controller means includes:

means for determining if an incoming call received over the telephone circuit through said first modem is a call authorized to communicate with the computer;

means for activating said second modem in response to said means for determining determining that the incoming call is authorized to communicate with the computer; and

means for deactivating said first modem in response to said means for determining determining that the incoming call is not authorized to communicate with the computer.

3. A system as defined in claim 2, wherein said means for activating said second modem includes means for generating and transmitting a call signal to said second modem.

4. A system as defined in claim 3, wherein said controller means further includes:

means for generating and transmitting a voice response through said first modem in response to said first modem receiving any incoming call; and

means for transmitting a carrier signal from said second modem through said first modem in response to said second modem receiving said call signal.

5. A system as defined in claim 4, wherein said means for determining includes:

signal decode means for decoding analog signals, transmitted in the incoming call, into corresponding digital signals;

entry code select means for selectably defining an entry code; and

entry code compare means, responsive to said signal decode means and said entry code select means, for determining whether said corresponding digital signals designate said entry code.

6. A system as defined in claim 1, wherein said controller means includes:

signal decode means for decoding analog signals, transmitted in an incoming call, into corresponding digital signals;

entry code select means for selectably defining an entry code; and

entry code compare means, responsive to said signal decode means and said entry code select means, for determining whether said corresponding digital signals designate said entry code.

7. A system as defined in claim 6, wherein said controller means further includes:

means for generating and transmitting a voice response through said first modem in response to said first modem receiving any incoming call; and

means for transmitting a carrier signal from said second modem through said first modem in response to said entry code compare means determining that said corresponding digital signals designate said entry code.

8. A system as defined in claim 1, wherein said controller means includes:

means for generating and transmitting a voice response through said first modem in response to said first modem receiving any incoming call; and

means for transmitting a carrier signal from said second modem through said first modem in response to a validated incoming call being received through said first modem.

9. A system as defined in claim 1, wherein said controller means includes:

timer means, connected to said first modem, for detecting the expiration of a predetermined timing period commenced in response to an incoming call received through said first modem over the telephone circuit; and

means, connected to said timer means, for generating an internal call and for transmitting said internal call to said second modem in response to expiration of the predetermined timing period so that upon answering said internal call the computer is in communication with the telephone circuit through both said second modem and said first modem.

10. A method of protecting a computer system connected into a telephone circuit from unauthorized calls, said method comprising the steps of:

answering through a first modem an incoming call before the call is received by the computer system, which incoming call is initiated from a calling end and transmitted over the telephone circuit to the first modem;

detecting whether a predetermined event occurs after the incoming call is answered by the first modem; and

transferring through a second modem the incoming call to the computer system only if the predetermined event occurs and is detected so that communication between the computer system and the telephone circuit occurs through both of the first and second modems.

11. A method as defined in claim 10, further comprising the step of transmitting a voice response over the telephone circuit when the incoming call is answered by the first modem.

12. A method as defined in claim 10, wherein said step of detecting includes determining if a predetermined time period after the incoming call is answered by the first modem expires before the incoming call is terminated from the calling end so that the predetermined event upon which the incoming call is transferred is defined as the expiration of the time period without the incoming call being terminated.

13. A method as defined in claim 10, wherein said step of detecting includes determining if a plurality of dual-tone multiple-frequency signals are transmitted from the calling end in a preselected sequence after the incoming call is answered.

14. A system for connecting a computer with an incoming call over a telephone circuit, said system comprising:

a first modem connected to said telephone circuit for answering said incoming call without emitting an audible carrier tone;

a second modem connected to said computer;

controller means, connected to said first modem and said second modem, for controlling said second modem in response to a valid incoming call being received through said first modem so that said computer is communicated through both said second modem and said first modem to said telephone circuit to receive said valid incoming call, said controller means comprising;

timer means for detecting the expiration of a predetermined timing period commenced in response to said first modem answering said incoming call, said timer means generating a time signal indicating that said timing period has expired, and

a modem ring circuit, responsive to said time signal, which generates an internal call to said second modem upon receiving said time signal so that, upon answering said internal call, said second modem and said computer are in communication with said telephone circuit through said first modem; and

means, connected between said computer and said first and second modems, for disconnecting said modems from said valid incoming call when said first modem, said second modem, and said computer are all in communication with said telephone circuit and an incorrect password is transmitted in said incoming call.

15. A system for connecting a computer with an incoming call over a telephone circuit, said system comprising:

a first modem connected to said telephone circuit for answering said incoming call without emitting an audible carrier tone;

a second modem connected to said computer;

controller means, connected to said first modem and said second modem, for controlling said second modem in response to a valid incoming call being received through said first modem so that said computer is communicated through both said second modem and said first modem to said telephone circuit to receive said valid incoming calls, said controller means comprising;

a dual tone multiple frequency decoder for decoding analog signals, transmitted in said incoming call, into corresponding digital signals,

entry code select means for selectably defining an entry code,

entry code compare means, responsive to said signal decoder and said entry code select means, for determining whether said digital signals designate said entry code,

a modem ring circuit, responsive to said entry code compare means determining that said digital signals designate said entry code, for generating an internal call and for transmitting said internal call to said second modem, so that upon answering said internal call, said second modem and said computer are in communication with said telephone circuit through said first modem,

a modem hang-up circuit, responsive to said entry code compare means determining that said digital signals do not designate said entry code, for disconnecting said first modem from said incoming call, and

means for generating and transmitting a voice response through said first modem upon said first modem receiving said incoming call and before said second modem and said computer are in communication with said telephone circuit through said first modem; and

means, connected between said computer and said first and second modems, for disconnecting said modems from said incoming call when said first modem, said second modem, and said computer are all in communication with said telephone circuit and an incorrect password is transmitted in said incoming call.