The shadowy techniques used by some journalists and private detectives to obtain confidential information are once again under the spotlight.
Many people were astonished to learn how easy it could be to hack into mobile phone voicemails after the arrest of the News of the World's royal editor, Clive Goodman, in August 2006.
This is a relatively straightforward process if the phone's owner has not changed their Pin number, industry experts said at the time.
The Old Bailey heard that a private detective working for Goodman had posed as a credit controller to trick telephone companies into switching people's Pin codes to default numbers, thereby enabling access to their voicemails.
He then passed the Pin numbers on to the journalist so he could listen to the messages.
This is easier than hacking into live mobile phone conversations, which has happened to members of the Royal family in the past but is now much harder because of new digital technology.
A report published by the Information Commissioner's Office (ICO) in May 2006 called What Price Privacy? also described how unscrupulous private investigators "blag" their way to getting confidential data.
It said: "Suppliers use two main methods to obtain the information they want: through corruption, or more usually by some form of deception, generally known as 'blagging'.
"Blaggers pretend to be someone they are not in order to wheedle out the information they are seeking. They are prepared to make several telephone calls to get it.
"Each call they make takes them a little bit further towards their goal - obtaining information illegally which they then sell for a specified price.
"Records seized under search warrants show that many private investigators and tracing agents are making a lucrative profit from this trade."
Investigators have found blagging "training manuals" while searching the offices of some private detectives, the ICO said.
One such document, found in Middlesex, took newcomers to the method "diligently and with a certain wry cunning" through wide-ranging sources of information, from next-door neighbours to utility companies.
The manual stressed the importance of using correct jargon, maintaining a confident approach, and employing psychology.
Its advice on tricking staff at the old Department of Social Security read: "The way to con this type of person is to convince them that you are just as prim and proper as they are.
"Don't even bother calling them under the pretext that you are a cockney or an idiot, because you won't last five seconds.
"They deal with idiots and layabouts all day, so ring them in the style of a keen little civil servant who wants to learn to solve their problems instead of relying on senior staff at another office. Speak with a clear, confident manner.
"Be polite and friendly at all times as rudeness will not work here."
The manual concluded with over 15 pages of "frighteningly plausible" example scripts to use when trying to obtain information from a telephone call, the ICO said.Reuse content