[ Pobierz całość w formacie PDF ]
.On offer are news services from the world's great pressagencies, commercial and maritime messages, meteorological data, andplenty of heavily-encrypted diplomatic and military traffic.Avariety of systems, protocols and transmission methods are in use andthe hacker jaded by land-line communication (and perhaps for themoment put off by the cost of phone calls) will find plenty of fun onthe airwaves.The techniques of radio hacking are similar to those necessary forcomputer hacking.Data transmission over the airwaves uses either aseries of audio tones to indicate binary 0 and 1 which are modulatedon transmit and demodulated on receive or alternatively frequencyshift keying which involves the sending of one of two slightlydifferent radio frequency carriers, corresponding to binary 0 orbinary 1.The two methods of transmission sound identical on acommunications receiver (see below) and both are treated the same fordecoding purposes.The tones are different from those used onland-lines--'space' is nearly always 1275 Hz and 'mark' can be one ofthree tones: 1445 Hz (170 Hz shift--quite often used by amateurs andwith certain technical advantages); 1725 Hz (450 Hz shift--the onemost commonly used by commercial and news services) and 2125 Hz (850Hz shift--also used commercially).The commonest protocol uses the5-bit Baudot code rather than 7-bit or 8-bit ASCII.The asynchronous,start/stop mode is the most common.Transmission speeds include: 45baud (60 words/minute), 50 baud (66 words/minute), 75 baud (100words/ minute).50 baud is the most common.However, manyinteresting variants can be heard--special versions of Baudot fornon- European languages, error correction protocols, and variousforms of facsimile.The material of greatest interest is to be found in the highfrequency or 'short wave' part of the radio spectrum, which goes from2 MHz, just above the top of the medium wave broadcast band, throughto 30 MHz, which is the far end of the 10-meter amateur band whichitself is just above the well-known Citizens' Band at 27 MHz.** Page 99The reason this section of the spectrum is so interesting is that,unique among radio waves, it has the capacity for world-widepropagation without the use of satellites, the radio signals beingbounced back, in varying degrees, by the ionosphere.This specialfile:///E|/Books/Hackers Handbook.htm (94 of 133) [11/28/2000 5:58:50 AM] Hacker's Handbookquality means that everyone wants to use HF (high frequency)transmission--not only international broadcasters, the propagandaefforts of which are the most familiar uses of HF.Data transmissioncertainly occurs on all parts of the radio spectrum, from VLF (VeryLow Frequency, the portion below the Long Wave broadcast band whichis used for submarine communication), through the commercial andmilitary VHF and UHF bands, beyond SHF (Super High Frequency, justabove 1000 MHz) right to the microwave bands.But HF is the mostrewarding in terms of range of material available, content ofmessages and effort required to access it.Before going any further, hackers should be aware that in a numberof countries even receiving radio traffic for which you are notlicensed is an offence; in nearly all countries making use ofinformation so received is also an offence and, in the case of newsagency material, breach of copyright may also present a problem.However, owning the equipment required is usually not illegal and,since few countries require a special license to listen to amateurradio traffic (as opposed to transmitting, where a license is needed)and since amateurs transmit in a variety of data modes as well,hackers can set about acquiring the necessary capability withoutfear.EquipmentThe equipment required consists of a communications receiver, anantenna, an interface unit/software and a computer.Communications receiver - This is the name given to a good qualityhigh frequency receiver.Suitable models can be obtained,second-hand, at around 100; new receivers cost upwards of 175.There is no point is buying a radio simply designed to pick upshortwave broadcasts which will lack the sensitivity, selectivity andresolution necessary.A minimum specification would be:Coverage 500 kHz--30 MHzResolution >100 Hz** Page 100Modes AM, Upper Side Band, Lower Side Band,CW (Morse)Tuning would be either by two knobs, one for MHz, one for kHz, orby keypad [ Pobierz całość w formacie PDF ]
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.On offer are news services from the world's great pressagencies, commercial and maritime messages, meteorological data, andplenty of heavily-encrypted diplomatic and military traffic.Avariety of systems, protocols and transmission methods are in use andthe hacker jaded by land-line communication (and perhaps for themoment put off by the cost of phone calls) will find plenty of fun onthe airwaves.The techniques of radio hacking are similar to those necessary forcomputer hacking.Data transmission over the airwaves uses either aseries of audio tones to indicate binary 0 and 1 which are modulatedon transmit and demodulated on receive or alternatively frequencyshift keying which involves the sending of one of two slightlydifferent radio frequency carriers, corresponding to binary 0 orbinary 1.The two methods of transmission sound identical on acommunications receiver (see below) and both are treated the same fordecoding purposes.The tones are different from those used onland-lines--'space' is nearly always 1275 Hz and 'mark' can be one ofthree tones: 1445 Hz (170 Hz shift--quite often used by amateurs andwith certain technical advantages); 1725 Hz (450 Hz shift--the onemost commonly used by commercial and news services) and 2125 Hz (850Hz shift--also used commercially).The commonest protocol uses the5-bit Baudot code rather than 7-bit or 8-bit ASCII.The asynchronous,start/stop mode is the most common.Transmission speeds include: 45baud (60 words/minute), 50 baud (66 words/minute), 75 baud (100words/ minute).50 baud is the most common.However, manyinteresting variants can be heard--special versions of Baudot fornon- European languages, error correction protocols, and variousforms of facsimile.The material of greatest interest is to be found in the highfrequency or 'short wave' part of the radio spectrum, which goes from2 MHz, just above the top of the medium wave broadcast band, throughto 30 MHz, which is the far end of the 10-meter amateur band whichitself is just above the well-known Citizens' Band at 27 MHz.** Page 99The reason this section of the spectrum is so interesting is that,unique among radio waves, it has the capacity for world-widepropagation without the use of satellites, the radio signals beingbounced back, in varying degrees, by the ionosphere.This specialfile:///E|/Books/Hackers Handbook.htm (94 of 133) [11/28/2000 5:58:50 AM] Hacker's Handbookquality means that everyone wants to use HF (high frequency)transmission--not only international broadcasters, the propagandaefforts of which are the most familiar uses of HF.Data transmissioncertainly occurs on all parts of the radio spectrum, from VLF (VeryLow Frequency, the portion below the Long Wave broadcast band whichis used for submarine communication), through the commercial andmilitary VHF and UHF bands, beyond SHF (Super High Frequency, justabove 1000 MHz) right to the microwave bands.But HF is the mostrewarding in terms of range of material available, content ofmessages and effort required to access it.Before going any further, hackers should be aware that in a numberof countries even receiving radio traffic for which you are notlicensed is an offence; in nearly all countries making use ofinformation so received is also an offence and, in the case of newsagency material, breach of copyright may also present a problem.However, owning the equipment required is usually not illegal and,since few countries require a special license to listen to amateurradio traffic (as opposed to transmitting, where a license is needed)and since amateurs transmit in a variety of data modes as well,hackers can set about acquiring the necessary capability withoutfear.EquipmentThe equipment required consists of a communications receiver, anantenna, an interface unit/software and a computer.Communications receiver - This is the name given to a good qualityhigh frequency receiver.Suitable models can be obtained,second-hand, at around 100; new receivers cost upwards of 175.There is no point is buying a radio simply designed to pick upshortwave broadcasts which will lack the sensitivity, selectivity andresolution necessary.A minimum specification would be:Coverage 500 kHz--30 MHzResolution >100 Hz** Page 100Modes AM, Upper Side Band, Lower Side Band,CW (Morse)Tuning would be either by two knobs, one for MHz, one for kHz, orby keypad [ Pobierz całość w formacie PDF ]