A last operational point that bedevils communications intelligence is'retention'--the preservation of intercepted signals for short or longperiods of time until they can be processed, cryptanalyzed, interpreted,or used. As we have noted, storing a signal that the holder is unableto restore to its original form typically takes far more memory thanstoring an understandable signal. This is justified because, encipheredmessages can be of value even if they are first read only months oryears after they were originally sent. During World War II, Alliedcryptanalysts were sometimes weeks or even months behind on someclasses of traffic (Welchman 1982). Some signals intercepted duringthe Cuban missile crisis of 1962 were not read until two yearslater (Hersh 1987). In what is probably the granddaddy of ciphertextlongevity, Soviet messages sent in the 1940s were still being studiedin the 1970s (Wright 1987). Managing the storage of intercepted materialis thus a major problem in all signals intelligence activities.
After all of the technical processes characteristic of communicationsintelligence, the 'product' enters in to the part of the process commonto information from all intelligence sources: interpretation, evaluation,dissemination. One process looms larger over comint than over perhapsany other intelligence material: 'sanitization'--removal from theintelligence product of information that would reveal its sources.Sanitization to greater or lesser degrees produces intelligence ofvarying levels of classification.
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The 'sine qua non' of communications intelligence is acquisition of signals. Without communications in the form of radio waves, electrical currents in wires, written materials, or copied disks and tapes, there can be no work for cryptographic or intelligence analyst. The interception of communications presents both a strategic and a tactical aspect.
Strategically, it is crucial to learn as much as one can about an opponent's communications infrastructure. The first step is to come up with the most precise possible description of the target--what the military call the 'order of battle'. If the target is a country, it may have millions of residents who in turn make millions of phone calls every days. Most of these calls are not of interest; the people who make them do not work for the
government or in critical industries and say little of intelligence value.
Describing the target is one of the many areas where 'collateral intelligence-information from sources other than covert interception of communications plays a vital role. Most of the information about a country and its government can be learned from open sources, such as phone books, newspapers, histories, and government manuals. Some, however, will come from covert sources such as spies, and some will come from communications intelligence itself.
Strategically, it is crucial to learn as much as one can about an opponent's communications infrastructure. The first step is to come up with the most precise possible description of the target--what the military call the 'order of battle'. If the target is a country, it may have millions of residents who in turn make millions of phone calls every days. Most of these calls are not of interest; the people who make them do not work for the
government or in critical industries and say little of intelligence value.
Describing the target is one of the many areas where 'collateral intelligence-information from sources other than covert interception of communications plays a vital role. Most of the information about a country and its government can be learned from open sources, such as phone books, newspapers, histories, and government manuals. Some, however, will come from covert sources such as spies, and some will come from communications intelligence itself.
Once the targets have been precisely identified, it is necessary to discover how they communication with one another. Are their communications carried by high-frequency radio, by satellite, or by microwave? How accessible the communications are and how they can be acquired is a function of the means
chosen. High-frequency radio and satellite transmissions are the most accessible.
At the time of World War II, most radio communications and thus most of what was intercepted was HF. Such signals bounce back and fourth between the ionosphere and the ground and can travel thousands of miles. This property
makes intercontinental radio communication possible; at the same time, it makes it essentially impossible to keep HF signals out of the hands of opponents. Today a large fraction of radio communication is carried by satellite. Satellite downlinks typically have 'footprints' thousands of miles across that spread over more than one country. Terrestrial microwave
communications are significantly harder to intercept. They travel between towers a few miles or tens of miles apart. Intercept facilities on the ground must generally be located within a few tens of miles of the micro-wave path and often require facilities in the target country. In the 1970s
and the 1980s, there was a war of words between US and Soviet diplomats over Soviet microwave interception activities from a residence the Soviet maintained at Glen Cove, New York (Broad 1982).
As with the organization structure, a target's communication practices can often be derived from open sources. Since national and international organizations cooperate in allocating the radio spectrum, it is easier to identify the frequencies used for military, police, or air traffic control communications by consulting regulations and standards than by direct spectrum monitoring.
chosen. High-frequency radio and satellite transmissions are the most accessible.
At the time of World War II, most radio communications and thus most of what was intercepted was HF. Such signals bounce back and fourth between the ionosphere and the ground and can travel thousands of miles. This property
makes intercontinental radio communication possible; at the same time, it makes it essentially impossible to keep HF signals out of the hands of opponents. Today a large fraction of radio communication is carried by satellite. Satellite downlinks typically have 'footprints' thousands of miles across that spread over more than one country. Terrestrial microwave
communications are significantly harder to intercept. They travel between towers a few miles or tens of miles apart. Intercept facilities on the ground must generally be located within a few tens of miles of the micro-wave path and often require facilities in the target country. In the 1970s
and the 1980s, there was a war of words between US and Soviet diplomats over Soviet microwave interception activities from a residence the Soviet maintained at Glen Cove, New York (Broad 1982).
As with the organization structure, a target's communication practices can often be derived from open sources. Since national and international organizations cooperate in allocating the radio spectrum, it is easier to identify the frequencies used for military, police, or air traffic control communications by consulting regulations and standards than by direct spectrum monitoring.
