The risks may be high, but the rewards are big. In a cut-throat tabloid market, with ever-shrinking circulations, hitting the jackpot with a genuine showbiz or royal scoop is viewed as a sure-fire way of boosting sales and, if secured by a freelancer, a megabucks payday.
No wonder then, says one security consultant, that there is a thriving and secretive cottage industry, which applies the tricks and scams used in the security trade to celebrity muckraking.
"We shouldn't be at all surprised that this sort of thing is happening in tabloid newspapers. In the corporate world, covert intelligence-gathering and bugging has been absolutely rife for years," he says.
The charges against the UK Sunday tabloid newspaper News of the World's royal editor, Clive Goodman, and the soccer player-turned-private investigator, Glenn Mulcaire, cast light on an area of journalism that tabloid bosses would far rather remained in the murky back-rooms: the use of private investigators to do much of the dirty -- and illegal -- grunt-work of celebrity scoop-getting.
That includes the widespread practice of purchasing personal details via rogue car-clamping companies, who can access data via Britain's Driver and Vehicle Licensing Agency, and corrupt mobile phone company employees, as well as phone-tapping, hacking into text and voice messages, accessing phone records and bank statements, and compiling photographic evidence through surveillance.
Crucially, according to one tabloid source, news executives -- and the well-known writers who may use the information in their copy -- maintain plausible deniability about the methods employed to gather it, especially when laws are broken, by keeping the commissioning process and contacts with investigators at arm's length. This is usually done by a designated reporter or third party.
Several entertainment industry PRs have been crying foul over tabloid dirty tricks for years. James Herring of Taylor Herring PR, whose clients include singer Robbie Williams, says it started with newspapers accessing celebrities' mobile phone voicemail by using the default factory-setting security codes.
"The first time we saw it really go up a gear, though, was when we were handling the John Leslie debacle [in which a TV presenter faced allegations of rape]. During that weekend where he was massively under siege, he found that he couldn't get into his mobile phone messages. What had happened was that a journalist had accessed his messages, discovered that he was still using the default pin code and reset it with a new pin number so that it froze him out of his own messages, which was eye-opening in terms of what we were up against," Herring said.
Intriguingly, Herring claims things have taken another twist in the past month.
"The latest trick is for someone to ring up a celebrity, posing as someone from their mobile phone network or whatever, saying they want to send some sim updates to their phone so that they can access the latest messaging technology. Then they ask for the person's pin code for verification. This is currently the source of a huge amount of tabloid stories," he said.
Herring describes such tactics as "a digital form of rifling through people's bins."
"Mobile phones have a lot to answer for, not just in terms of this pin-number hacking, but also in other respects. Photo-messaging and video-messaging have effectively equipped journalists -- and people providing them with material -- with a whole new set of tools which enables them to gather evidence on the hoof and on the spot," he says