A new study from an online watchdog group shows a surge in complaints that hackers are manipulating both adult and regular business sites to spread viruses and images of children being sexually assaulted.

According to the BBC, the group, the Internet Watch Foundation (IWF), has tracked 227 reports of use of "orphan folders" to hide the offending material in the past six weeks.

"We hadn't seen significant numbers of hacked websites for around two years, and then suddenly in June we started seeing this happening more and more," IWF researcher Sarah Smith said in a statement on the group's website. "We speculate that the motivation behind the hacking is to distribute malware, specifically a Trojan."

The IWF said on its website on Monday that the malware is spread when users on targeted adult websites land on certain images or videos linked to the folders, which are hidden on other business sites. One example involved a furniture store site being used as a repository for the images of sexual abuse.

A British web security specialist, Graham Cluley, speculated to The Independent that the scheme may seek to take advantage of the country's new "opt-in" policy toward accessing adult content on home computers in order to blackmail people who fall victim to the scam.

"What better way to scare someone into paying a ransom than to tell them that they have been spotted accessing child pornography?" Cluley told the Independent. "Many people who receive a message like that would be petrified of contacting the police to check if it's true, or taking the computer down to PC World to be checked over."

[Image via Agence France-Presse]