Seizing the Epilepsy Attack

I may be a couple of days late with this one, but this is one of those few times, when I am truly amazed by the malicious intent of an internet exploit. Hackers defacing a website, frequented by epileptics, to intentionally cause seizures.

Epilepsy, a chronic neurological disorder, with a prevalence of approximately 1 in 100 (3 million people) is characterized by a storm of abnormal electrophysiological activity in the brain. Normal cognitive function is temporarily disrupted, due to this excessive firing, and hypersynchronous discharge of cortical neurons. The results of this disturbance, commonly known as a seizure, are episodic occurrences for people with epilepsy. The clinical appearance depends on the extent and region of brain involvement, but can range from headaches to violently uncontrolled muscle spasticity.

Seizures are often elicited by a stimulus or event. Photic induced seizures, are those triggered by visual stimuli. These usually appear as flashing or flickering light, in both contrasting solids (photosensitive) and certain geometric patterns (pattern-sensitive). Individual characteristics are known, which lower the threshold for inducing seizures. Specifically, the effectiveness increases with brightness and contrast ratio, and is most potent at flash rates between 15-25 Hz.

The Epilepsy Foundation, a non-profit organization with 53 national affiliates, is an agency that conducts numerous programs to help those afflicted with epilepsy. Last weekend, their eCommunities forum section was hacked. These forums provided a community support network for people to discuss various topics related to living with epilepsy. Like most forums, interaction consisted of posting questions and answers within a topic group. Viewing the forum source, reveals that it's Cold Fusion based and apparently, allows HTML to be embedded into user postings. Hackers exploited this function and used JavaScript to manipulate several links in this section of their site. Unsuspecting users, found themselves clicking on forum messages, which contained flashing animated gifs, providing the visual trigger for seizures in photosensitive epileptics. Following that incident, they used a redirection attack, which sent forum users to sites containing flashing patterns, targeting pattern-sensitive individuals as well.

This is not the first time that flickering visual imagery from a TV or computer monitor have induced seizures. In 1981 there was a case of "Space Invader Epilepsy" reported in the Lancet medical journal. During the late 80's through the mid-90's, several cases of video game and TV related seizures were reported, due to their display of flashing imagery. In December of 1997, a four second rocket launch sequence, from the Japanese cartoon, Pokémon, consisted of flashing blue and red light. This resulted in the hospital treatment of 685 children, for related symptoms, approximately 80% of which were seizures.

However, this is the first time that this was carried out intentionally. This has also been reported as, the first type of internet based attack, that has caused direct physical harm to the end user. This is truly a new low in malicious activity carried out online. It's hard to categorize the legal classification for this act, in terms of cyber-crime. However, it should be considered a form of physical assault. I can understand the mindset of the criminal hacker with financial motives, but this cruel misuse of the internet is beyond logical comprehension. Unfortunately, without any financial loss or theft of personal information, this crime will probably not be extensively pursued by the authorities.

So, how can one protect themselves from these types of attacks?

In this case, there are two options. Block any content that displays a trigger stimulus, or prevent the exposure of such material to the individual.

While production guidelines and pre-screenings have been employed for years, to prevent potential hazards from video games and TV, this would not prevent the kind of incident displayed last week.

In this case, a form of proactive and defensive security must be utilized. Research is being conducted into automated screening algorithms, which would monitor the timing sequence, brightness and contrast of internet imagery. If it detected content that met the predetermined parameters for seizure stimulation, it would be blocked prior to presentation on the users monitor. Furthermore, adaptive temporal filters have been developed for attenuation of flickering imagery. These automated self adjusting displays, change their output refresh rate to accommodate a wide range of originating frequencies. Lastly, research in visual perception, has produced several types of cross-polarized glasses and lens filters, which act as optical shields, to the offending stimuli. These have been successful at seizure prevention by reducing the roles that color modulation and contrast have, as stimulus triggers.

Although, these security methods place the burden on the affected individuals-a responsibility they should not bear. They are temporary defensive measures, not long term solutions.

The security community primarily focuses on protecting the network infrastructure and the data it carries, as these are the targets of attack. But when the system we are protecting, is used as an instrument of physical attack, perhaps we need to think about how to protect the most important element of the internet....people.

Any ideas or solutions? Send them to: