Suspected paedophiles as young as 13 years old have been arrested on Tuesday by the largest proactive investigation ever undertaken in the UK to crack down on Internet child pornography. Forty-three search warrants were executed Tuesday morning by the Obscene Publications Unit at Greater Manchester police. The dawn raids, dubbed Operation Appal, have resulted in 24 successful arrests to date, with one suspect aged just 13. "In operations of this nature, you don't ever know the profile of the person on the other end of the computer. We have arrested a number of young people -- we suspect one boy as young as 13 of distributing child pornography," said inspector Terry Jones at Manchester's Obscene Publications Unit. "That's a surprise to me and very disturbing." Jones co-ordinated the UK wide investigation and explains that arrests were not the main point of the exercise. "The primary objective was to seize secure computer-based evidence. The arrests are of significance, but the operation was all about securing evidence," he said. Computers were seized from every house that was searched. Jones said that at one address, the occupant admitted to holding one gigabyte of child porn on his computer's hard drive, and attempted to smash CD-ROM's holding damaging evidence with a hammer. Operation Appal is the third investigation launched by the Greater Manchester police force into the distribution of obscene material over the Internet. Jones explains that in his experience, the task of proving who is responsible for the paedophile evidence found on a computer hard-drive is usually not a problem -- there has only been one case to date of a person pleading "not guilty" to the crime. "It is very difficult for a person to avoid responsibility for possession [of child pornography] once evidence has been found on their hard-drive, " said Jones. "A lot of people treat their computer as their friend, and confide in it, and tie themselves to it," he added. The operation that began three months ago was co-ordinated in conjunction with filtering software manufacturer SurfControl. "The software enabled us to focus on this activity more efficiently and detect more offenders than we'd ever be able to do manually," explained Jones. According to reports from SurfControl, the software reduced the number of man-hours needed to produce a suspect by a factor of ten. Paedophile activity on the Internet in the form of exchanging indecent images of children is growing rapidly. In 1995 the Greater Manchester Unit seized a total of 12 indecent images, but by 1999 the figure was 41,000 -- all but three in digital form. On 2 September 1998 an international police operation involving 12 countries successfully seized nearly a million child porn images as well as 1,800 digital videos depicting children being sexually abuse. Seven British paedophiles were jailed in February for their involvement in the so-called Wonderland Club, given sentences ranging from 12 to 30 months. No one received the maximum possible sentence of three years. What are the risks of paedophiles approaching my children through Yahoo! Messenger chatrooms? Find out the details of ZDNet News' investigation in the Chatroom Danger Special Report After the publication of the ZDNet news' special report -- "Chatroom Danger". Our readers responded on the forums with many views and opinions on the subject. Jane Oliver has gathered some of them here and poses the question -- Wouldn't stamping out the dangers just take a good helping of common sense all round? Go to AnchorDesk UK for the news comment. Are your children in danger on the Internet? Find out with the Web of Porn Special Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read other letters.