Crime gangs are contributing to a surge in internet child porn, according to the national criminal intelligence service's (NCIS) annual assessment of serious and organised crime.
The study, published today, says the number of websites showing child porn - often featuring images of what is believed to be actual abuse - rose by 64% last year.
The NCIS report says most child sex offenders act alone or in secretive networks that distribute images freely. But the potential profits to be made from selling images of child abuse online have also attracted "serious and organised criminals".
This has enabled a "rapid growth in the publication of computer-based images of child abuse and their global distribution". As a result, computer-based images of child abuse have now largely replaced printed material.
Internet chat rooms and exclusive websites also encourage "extensive criminal networking", where individuals exchange indecent images and fantasies and help each other gain access to victims.
Such virtual meeting places help "justify and normalise offending" by providing positive reinforcement that child pornography is acceptable.
The internet has changed the "nature and extent" of paedophile networks, with sites offering participants "online guides" to all aspects of child sex.
"The internet makes it possible to network on a much wider scale and, if security measures are taken, with less risk," says the report.
"Some (of the guides) have hyper-links to bulletin boards, information about chat rooms, where IT expertise and access or grooming techniques are shared, and passwords or pass-phrases given to access pornography."
The report says that most online child sex networks are hierarchical in structure and secretive, with access by invitation only. Individuals may be approached in chat rooms and invited to join a network.
Often there is a vetting process, with status and trust gained by members through evidence of illegal activity.
"Protecting themselves against law enforcement is a key concern, and some online child sex offenders openly discuss methods for keeping their activities from the police," the report says.
There is also evidence that online networks undertake "counterintelligence activity", researching techniques used by the police and internet watch groups by debriefing people who have been arrested.
Some members are aware of surveillance techniques and take steps to avoid being followed.
If an offender puts members of the network at risk, perhaps by the unauthorised passing on of images, he is likely to have his computer targeted with viruses or denial of service attacks.
Possible the most alarming development is the sophisticated use of the internet by paedophiles to target and groom potential victims in internet chatrooms.
"The anonymity of the internet allows adult offenders to misrepresent themselves as young children or more often teenagers, making it easier for them to establish a bond.
"In some cases, children have been duped into meeting up with offenders, who have then attempted to abuse them sexually, sometimes successfully."
The report cites intelligence supplied to police by the Internet Watch Foundation (IWF), that over half of all illegal websites known to the IWF are hosted in the US, although the number in Russia has more than doubled (from 286 to 706).
"This creates significant difficulties for law enforcement, not least in identifying and tracing the victims who feature in images of child abuse. Often there are no leads for research into the victims' identity or the location of the abuse," says the report.
