Paedophiles are using new methods to hide child abuse images in what look like legitimate web stores.
This tactic is becoming more prevalent online, according to a report from the Internet Watch Foundation (IWF) which was highlighted by the BBC.
The IWF's report for 2011 revealed the fact that sex offenders are "disguising" websites so that they appear as if they contain legal content, but should a user access a "predetermined path" which takes them to the site, they will instead be able to view images of child abuse.
Some members of the public have apparently stumbled on these hidden caches of images by accident, and have reported them to the IWF. Such tactics of concealment are making life more difficult for those engaged in the fight against online child pornography.
The IWF notes that this particular technique was witnessed some 600 times last year. These disguised sites have not been found on UK servers.
There was some more positive news, however, in that when material is found in the UK, the online industry is becoming more efficient at getting rid of it. The typical removal time is now less than an hour.
Chief Executive at the IWF, Susie Hargreaves, commented: "The IWF can, for the second year running, report successes with its work to speed up the time it takes to remove images and videos of online child sexual abuse."
"In particular, those companies and organisations which make up our membership are 40% quicker at removing this criminal content when it's hosted outside of the UK than non-Members. However, our work continues with all those involved with the aim of eliminating online child sexual abuse content."