By Duncan Walker
BBC News Online
A computer database which can identify paedophiles and their victims within seconds has been unveiled by police.
Internet offenders could be tracked via the victims
The Childbase system uses sophisticated software to compare the faces of people in new abusive images with those in pictures already investigated.
If someone puts on weight or changes their hairstyle it can still recognise them and has already been able to identify the brothers and sisters of abuse victims.
By using the system to check whether there is a new victim or abuser, police believe it will help them focus on the most urgent cases.
Jim Gamble, Assistant Chief Constable of the National Crime Squad (NCS) which is behind the scheme, said Childbase had already saved children from abuse and that a "string of prosecutions" was being prepared.
Criminologist Professor John Grieve said "the bad guys are on their back foot", adding that the very technology they used for their crimes was being turned against them.
The Childbase system already contains 220,000 images of abuse, involving about 20,000 children from around the world.
Until now officers investigating pictures taken from suspects' computers have faced the slow and often traumatic process of looking through thousands of images to see if there is a link.
The system's ability to 'map' faces and turn them into a string of digits which can be compared against information already held means the process can now be completed almost instantly.
Andrew Williams of Canadian firm Imagis, which developed the tool, said: "It will look at the inner face and unless you take drastic surgical action it will find you."
The NCS is preparing to share the information and techniques with police in other countries, to fight what has become an international crime.
Mr Gamble said: "We are making the internet as safe as is humanly possible for our children.
"We are trying to make the global village an area we police in a global sense."
The tool will also be available to all British forces and will be used in Operation Ore, its investigation into more than 6,000 suspected internet paedophiles in the UK.
Details of exactly how the system works are being kept secret, as police believe it could help paedophiles learn how to escape its notice.
But Professor Grieve said that it was important to keep the pressure up, no matter how sophisticated child sex abusers become.
He said: "They're sophisticated enough to think of the next move, but you can't allow yourself to be paralysed.
"The NCS have show they're prepared to go to computer buffs, charities, victims' organisations and technological entrepreneurs and look for all kinds of solutions."
Shy Keenan, who was abused as a child and is in many images still on the internet, said: "This is an astonishing, groundbreaking breakthrough. This is going to change the face of child abuse on the internet."