Yes, it is possible for the powers that be to listen in on your mobile phone conversation.

The issue was brought to light by the accusations of the Thai army against a Thai telco last week. (See Stop Bugging Me!)

In fact, security agencies all over the world are snooping on mobile phone conversations even as you read this article, say telco security experts.

Although, admittedly, cellphone chats are harder to tap compared to those made on land lines.

According to Mr Ching Tim Meng, who works for consulting firm PIPC, legalised mobile phone taps or 'lawful intercepts' are carried out in countries like the United States, United Kingdom, Australia, and New Zealand, to catch criminals and terrorists.

'And I think it's a safe bet to say that most of the former Communist bloc countries are doing it, too - although I don't know whether it is done in Thailand or Singapore,' he said.

The Ministry of Home Affairs did not respond to enquiries by Digital Life by press time.

Unlike wiretaps of land lines in the past - in which surveillance teams attached a wire parallel to the phone line being tapped, so they could listen in on people's conversations - today's lawful intercept systems are much more sophisticated affairs.

Such systems are integrated into a telco's 'critical infrastructure', said Mr Ching, allowing the authorities to start their surveillance operations remotely, without going through the telco.

'This is more secure and minimises the chance of a security leak, like say, a criminal bribing someone at a telco to tell him which numbers are being bugged,' said an executive with a lawful intercept system vendor. He spoke on condition of anonymity due to 'political sensitivities at this current time'.

Lawful intercept systems are also heavily secured, both for security reasons as well as to prevent unauthorised users from tampering with the evidence collected.

Maintaining this 'chain of custody', the executive said, is necessary so that the data collected - which numbers are called, when the calls are made, their duration, and the actual audio recording of the call itself - can stand up in court.

In the US, given privacy concerns, lawful intercepts are only done as a last resort, he added.

Before law enforcement agencies begin the wire - or wireless - phone tapping, he said, they first have to convince a judge that they have exhausted all other options to gather intelligence about the subject in question.

Mr Ching said that modern lawful intercept systems cost US$5 million (S$7.6 million) upwards. They are made up of a combination of software, hardware and training for the team of people monitoring the calls.

That is not to say that lawful intercept systems are foolproof, said Mr Ching.

Countermeasures include special 'voice-scrambler' phones that encrypt the calls made on them - and are used by political heavyweights, financial hotshots, or those with something to hide, he said.

Such phones are incompatible with normal GSM phones like those from Nokia or Sony Ericsson, and cost anything from US$1,500 to US$1,800 each.

Stop bugging me!

LAST WEEK, THAI army chief General Sonthi Boonyarataglin accused telecommunications firm Advanced Info Services (AIS) of monitoring the conversations of military staff.

Gen Sonthi's allegation was refuted by an AIS spokesman, who said the company could not snoop on cellphones, and had no reason to do so anyway.

AIS was previously owned by deposed Thai premier Thaksin Shinawatra, before he sold his controlling stake of the firm to Singapore's Temasek Holdings. The sale sparked off widespread protests there, culminating in Mr Thaksin's fall from power.

Following Gen Sonthi's allegations, the military has switched mobile operators, and ordered staff to revert to older but more secure radio systems for sensitive communications.

The Thai parliament is also considering whether it should spend 6 billion baht (S$263 million) on a satellite for military and security purposes.