In what could be the first case of causing actual bodily harm via the internet, hackers have attacked the website of US charity Epilepsy Foundation by posting flashing images on to its forum pages.

Upon learning of the attack the Epilepsy Foundation closed the forum down, purged the offending images from the site and ramped up security. However, the attack did cause some adverse reactions from users.

"We are seeing people affected," Ken Lowenberg, a senior director at Epilepsy Foundation told Wired magazine. "It's fortunately only a handful. It's possible that people are just not reporting yet – people affected by it may not be coming back to the forum so fast."

'Anonymous' to blame?

It’s reported that the hackers initially used script to post hundreds of messages embedded with flashing GIF images. The attackers then switched to using JavaScript to redirect forum users to a page with a more complex image, designed to trigger seizures in both photosensitive and pattern-sensitive epileptics.

Wired also reports that there is “circumstantial evidence” linking the perpetrators of the attack to the loose-knit anti-Scientology collective, Anonymous. Earlier in the year Anonymous members were reported to be planning a mass attack on Scientology websites, although TechRadar denied this at the time.