the present invention provides a low - cost solution that directly prevents unauthorized use of a data network over voice channels . it prevents many direct attacks on receiving audio communication equipment by protecting directly against standard attacks that rely on the integrity of the data stream . for example , a standard buffer - overflow attack relies on being able to insert a small piece of valid machine code in a known location outside of the data buffer . this invention modifies the data stream to the point that this form of attack is not practical . by way of general overview , one embodiment of the present invention includes a computer having one or more network interfaces ( e . g ., high speed ) and a signal modification engine . the signal modification engine modifies audio streams in such a way as to be virtually undetectable to a human listener . the signal modification engine may work directly on the encoded audio data stream , or may optionally decode the audio data stream to a common format , introduce the modifications and re - encode the audio data stream to either the original format or a different format . the audio data stream modifications may include any or all of the following ( but are not limited to ): ( 1 ) introduction of a small quantity of “ white ” or audio noise , ( 2 ) introduction of a small amount of time dithering ( e . g ., expanding and contracting small time slices ), ( 3 ) introduction of a small amount of time dithering without modifying frequency content , ( 4 ) introduction of a small quantity of frequency shift noise , ( 5 ) introduction of a small quantity of phase shift noise , and ( 6 ) introduction of small changes in silence duration . in general , the audio data stream modifications can be treated as some generalized digital filter applied against the audio data stream with the objective of changing the underlying data bits without noticeably degrading the audio quality . the amount of degradation can be varied to suit the use and security requirements of the installation , i . e . controllable degradation . if an initial audio stream is true audio data , a human receiving the invention modified audio stream will , at worst , think that the telephone connection is not as clear as it should be . on the other hand , a random bit pattern ( of the present invention ) introduced into a virus in the process of being transferred will almost certainly prevent the virus from succeeding . fig1 is illustrative . in fig1 , a voip network 100 carries a subject voice data stream 102 initiated from a voip device 101 . the voice data stream 102 is indicative of a voice or audio communication ( e . g ., incoming or outgoing phone call ). in one embodiment , the voice data stream 102 is sent to or received by ( through a routing network 103 ) an invention voice data security system 104 for processing using a high - speed network interface ( not shown ). similarly , in another embodiment of the present invention , system 104 may have more than one high - speed network interface . the voice data security system 104 includes a signal modification engine 106 . the signal modification engine 106 is responsive to the received voice data stream 102 and modifies voice data stream 102 to a modified voice data stream 102 ′. after modifying voice data stream 102 , the signal modification engine 106 forwards ( through a routing network 103 ) the modified voice data stream 102 ′ to a voip device 108 . the voip device 108 can be a voip telephone and / or voip enabled computer system . in one embodiment , the voice data stream can be transmitted over the same routing network 103 . the routing network 103 can be the internet , intranet , or other known routing network . in another embodiment , after receiving the resulting voice data stream 102 ′, a computer system can establish a telephone connection such that the incoming / outgoing phone call can be received at a corresponding voip device 108 . thus , the signal modification engine 106 forwards ( through the routing network 103 ) the resulting ( modified ) voice data stream 102 ′ to a component of the network 100 for connection , i . e ., receiving the incoming / outgoing telephone call . it should be understood that the network 100 can be a bidirectional network or a unidirectional network . fig2 is a diagram of a voip network 200 employing voice data security of the present invention and using a firewall 202 to the direct voice data stream 102 . in one embodiment , the firewall 202 initially receives ( through the routing network 103 ) and then directs the voice data stream 102 to the signal modification engine 106 for security processing ( i . e ., modification ). after processing voice data stream 102 , the signal modification engine 106 can return the processed or modified voice data stream 102 ′ to the firewall 202 for forwarding or the signal modification engine 106 can forward the modified voice data stream 102 ′ directly . the firewall 202 or the signal modification engine 106 then directs the security processed / modified voice data stream 102 ′ to the appropriate destination in the same way as described for fig1 . fig3 is a flow diagram 300 of the signal modification engine 106 ( of fig1 ) process of modifying a voice data stream 102 . at step 302 , a voice data stream 102 exists on a network . the voice data stream 102 is received by the signal modification engine 106 in step 304 . upon receiving the voice data stream 102 , the signal modification engine 106 modifies the voice data stream 102 by introducing interferences or noise ( step 306 ) into the voice data stream 102 . at step 308 , the signal modification engine 106 delivers to an appropriate destination ( step 310 ); a modified voice data stream 102 ′ having audio differences . the amount of degradation of the audio differences is controllable . in this way , the voice data stream 102 is made secure without noticeably degrading audio quality . referring to fig1 and 2 , a voice data security system 104 employs a signal modification engine 106 to modify a voice data stream 102 by inserting noise or interference into the voice data stream 102 . an expanded view of the signal modification engine 106 is shown in fig4 . in one embodiment , as illustrated in fig4 , the signal modification engine 106 introduces a single interference or type of suitable noise . examples include , but are not limited to : ( 1 ) introduction of a small quantity of audio or white noise 406 , ( 2 ) introduction of a small amount of time dithering 408 for expanding and contracting small time slices , ( 3 ) introduction of a small amount of time dithering 408 for expanding and contracting small time slices without modifying frequency content , ( 4 ) introduction of a small quantity of frequency noise 410 , ( 5 ) introduction of small changes in silence duration 412 lengthening or shortening pauses , ( 6 ) introduction of a small quantity of phase shift noise 414 and ( 7 ) introduction of other types of interference 416 . known techniques for implementing these examples are employed . any combination of the foregoing and similar examples may be used by signal modification engine 106 . the amount of degradation ( in resulting audio / voice communication stream 102 ′) from applying these interferences can be varied ( controllable ) to suit the use and security requirements of the network 100 ( environment ). in this way , the present invention voice data security system 104 prevents many direct attacks on receiving audio communication equipment 108 , 110 , 112 and prevents unauthorized use of a data network via voice channels . fig5 shows an expanded view of a signal modification engine 502 that may decode and re - encode the voice data stream 102 during the process of generating a secured / modified voice data stream 102 ′. the signal modification engine 502 for the most part is similar to the signal modification engine 106 of fig4 . however , the signal modification engine 502 may decode the incoming voice data stream 102 in step 506 prior to introducing interferences 406 , 408 , 410 , 412 , 414 and / or 416 . for example , incoming voice data stream 102 is decoded into an audio wave form of certain or predetermined format , and then interferences 406 , 408 , 410 , 412 , 414 , and / or 416 are applied . after the signal modification engine 502 introduces the interference , the signal modification engine 502 may re - encode the modified voice data stream 102 ′ to the original format of the voice data stream 102 in step 520 . the resulting modified voice data stream 102 ′ is forwarded to the appropriate destination for voice / audio communication connection as described and shown in fig1 and 2 . in another embodiment , transcoding and transmogrification can be combined . the signal modification engine 502 re - encodes the modified voice data stream 102 ′ to a different encoding format ( at step 520 ). the resulting modified voice data stream 102 ′ in the different format is forwarded to the appropriate destination for voice / audio communication connection as shown in fig1 and 2 . in this way , the present invention is capable of providing secure voice data streams as well as reformatting the voice data stream for increased security if the encoding is randomly lossy . transcoding with a randomly lossy encoder without transmogrification may also be employed to introduce controlled degradation and hence voice data stream security of the present invention . it will be apparent to those of ordinary skill in the art that methods involved in the present invention may be embodied in a computer program product that includes a computer readable and usable medium . for example , such a computer usable medium may consist of a read only memory device , such as a cd rom disk or conventional rom devices , or a random access memory , such as a hard drive device or a computer diskette , having a computer readable program code implementing steps 304 , 306 and 308 of fig3 stored thereon . while this invention has been particularly shown and described with references to preferred embodiments thereof , it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims .