A walkie-talkie-sized scanner for listening to mobile phone calls on the 088 network, Garda, ambulance and fire-brigade calls is on sale in Dublin for under £200.
A scanner for listening to air-traffic control and shipping radio can be bought for less than £30. The user has to be at the airport or port to eavesdrop.
Certain Garda units can use secure channels, and many gardai use mobile phones for operational duties. But messages from Garda control on routine crimes, such as burglaries and assaults, and alarm calls are sent out to Garda radios on an easily-scanned analogue system. Only in the greater Cork Garda divisions is the analogue radio signal encrypted.
An £80 million plan to upgrade the Garda communication system to digital is to be put to the Cabinet for approval this month. The plan has been assessed and recommended by British consultants.
The Cork Garda system was replaced three years ago because the old system was on the point of collapse, a spokesman for the Department of Justice said. An optional encryption feature was added to the replacement system for Cork. It is a "stop-gap" measure until the introduction of a digital network across all Garda divisions.
Some scanners can monitor calls made on land-line cordless phones. By tuning in to the frequency an experienced scanner-operator near a house can use the scanner as a handset and make calls that are billed to the owner of the cordless phone.
A book listing all frequencies, including Garda frequencies and private numbers using cordless phones, is circulated among scanner enthusiasts and updated every six to eight months.
Users can programme a £160 scanner model, putting their favourite frequencies on 16 channels, to switch between them like a radio. More sophisticated scanners, costing up to £3,000, can be used to pinpoint a frequency and tune in to it in seconds.
Mr Liam Brady, a Dublin special investigator, sells surveillance equipment and trains people in counter-surveillance techniques. The equipment used for sweeping for listening devices is the same as that used to intercept calls.
It is not illegal to use a scanner, unless the intention is to commit a crime. Under the 1990 Larceny Act anyone having any article that can be used in a crime can be imprisoned for up to five years. Criminals using scanners can also be prosecuted for conspiracy to commit a crime.
"If you're standing on the Dublin Mountains you will pick up whatever is in the air," Mr Brady said. "The receiver does not have a range. It depends on the range of the transmitter sending out the signal." He uses a combination of two scanners, one of which can pick up signals on a wide band range between 30 Mhz and 2,000 Mhz and will pinpoint the most powerful signal in its immediate area.
Scanners have become a standard tool for drug dealers and other criminals. Most serious criminal gangs will have an electronics expert to monitor the communications of security forces. They are also used as standard by haulage and courier companies which are monitoring competing firms' calls.
The lack of security on police networks is a Europe-wide problem, as outdated technology is easily monitored. A new digital network, the Tetra system or Trans-European Trunked Radio, will replace most European analogue systems in the next decade. As this takes over as standard the operation of old analogue systems will become more difficult.
Technology already exists to monitor conversations on the digital mobile phone GSM network. The equipment costs £155,000, according to Mr Brady.
Using a laptop computer, the encrypted signal from a GSM mobile can be decoded if the listener is near the phone-user. The phone-tapper must be closer to the phone than the base-station used by the phone to bounce the signal. The signal is intercepted by the tapper as if it was a base-station and decoded before being sent on to the real base-station.
A Garda spokesman said the introduction of the £80 million upgrade was also dependent on the completion of the Esat mobile mast network, which has been delayed by objections by residents in areas where they are being erected.
