Attempts to access Cook's voicemail and that of his wife, and possibly hack his computer and intercept his post were also suspected.
Documents reportedly held by Scotland Yard show that "Mulcaire did this on the instructions of Greg Miskiw, assistant editor at News of the World and a close friend of Marunchak." The Metropolitan Police Service handled this apparent attempt by agents of the News of the World to interfere with a murder inquiry by having informal discussions with Rebekah Brooks, then editor for the newspaper.
Glenn Mulcaire had been Boyall's assistant, until the autumn of 2001 when the News of the World's assistant editor, Greg Miskiw gave him a full-time contract to do work for the newspaper.
This established that confidential information was illegally acquired from telephone companies, the Driver & Vehicle Licensing Agency and the Police National Computer.
Whittamore's network gave him access to confidential records at telephone companies, banks, post offices, hotels, theatres, and prisons, including BT Group, Crédit Lyonnais, Goldman Sachs, Hang Seng Bank, Glen Parva prison, and Stocken prison.
A number of arrests and convictions followed, most notably of the former News of the World managing editor Andy Coulson.
Murdoch and his son, James, were summoned to give evidence at the Leveson Inquiry.
The commissioner of London's Metropolitan Police Service, Sir Paul Stephenson, also resigned.
Advertiser boycotts led to the closure of the News of the World on 10 July 2011, after 168 years of publication.