A detective in the team who snared Facebook paedophile Paul Leighton said the case was the worst they have ever come across in their career.
Sunderland spray painter Leighton, 32, of Malvern Crescent, Seaham, was locked up for 16 years on Monday after admitting a range of sickening offences which included blackmailing youngsters into committing sex acts with relatives.
He was arrested after his phone was flagged up to national authorities last September as holding a number of indecent images.
Detective Sergeant Peter Morgan, part of the team who investigated Leighton,said: "Paul Leighton is one of the most serious offenders I have ever come across and his actions have had devastating impacts across the world.
"He has victims in this country, America, Canada, and Australia and there may be dozens more who have not yet reported abuse to the authorities.
"His offending has had a lasting impact on all the officers on the investigative team but from the minute Leighton was arrested he has shown no remorse for his actions.
"He was calculated and sophisticated in his approach to this abuse and his lack of thought for his victims is spine-chilling.
"Hundreds of families will never recover from the trauma of these offences and will have to live with what he has done to them for the rest of their lives.
"As for Leighton, he will spend a substantial part of his life behind bars where he cannot hurt anyone else - that is thanks to the hard work of our detectives.
"This case proves that we will work with law enforcement from across the globe to pursue abusers like Paul Leighton wherever they are and whoever they offend against."
James R. Mancuso, attaché for Homeland Security Investigations (HSI) in London, said: "Protecting children from exploitation is one of the most important missions we have, and as this case demonstrates, it takes the collaboration of law enforcement agencies around the world to tackle this crime.
"HSI is committed to working with partners like the Northumbria Police to arrest individuals who commit such heinous acts and ensure that they are prosecuted to the fullest extent of the law"
As part of the sentencing hearing, the court also heard statements from the mothers of two young girls abused by individuals blackmailed by Leighton.
A mother of a 16-year-old victim said: "She is very angry and anxious, she is terrified that he is going to come and get her. It breaks my heart that she feels that way, and I am at a loss how to cope with this."
"It angers me that she and our family have had to go through this and never ever thought that something like this would happen to us. The stress and anguish is never ending."
Another mother of a 14-year-old girl said: "She has lost a lot of confidence. It is very rare that you get a laugh or smile out of her. It is hard to watch."
Leighton pleaded guilty at an earlier hearing to three counts of rape, two sexual assaults on girls under 13, four counts of causing or inciting grooming, three counts of making and two counts of distributing indecent photographs, three counts of blackmail, one count of assault on a girl under 13 and one count of possessing a class B drug.
Anyone who feels like they have been a victim of a cyber-crime, or feels that they may have been groomed online, can contact police on 101 or Victims First Northumbria on 0800 011 3116.
Crime prevention advice about keeping safe online can be found on https://www.getsafeonline.org/