Attackers sent videos of flashing and strobing lights to people on Twitter last month as part of a cyberattack which deliberately targeted people with epilepsy.

The attacks targeted the Twitter feed of the Epilepsy Foundation, the organization said Monday.

Using the foundation’s handle and hashtags, the attackers posted videos and GIFs that used triggering light flashes. And they did it during National Epilepsy Awareness Month in November — when the greatest number of people with epilepsy would be following the account.

The Foundation identified at least 30 different accounts participating in the calculated action, Allison Nichol, the Epilepsy Foundation’s director of legal advocacy told CNN. The Foundation was not able to say how many people were affected by the attacks.

The Foundation said it has filed criminal complaints with law enforcement and will cooperate with them to ensure the attackers “are held fully accountable.”

The impact is serious

People with photosensitive epilepsy are sensitive to flashing lights or particular visual patterns that may trigger seizures, the Epilepsy Foundation says.

“While the population of those with photosensitive epilepsy is small, the impact can be quite serious. Many are not even aware they have photosensitivity until they have a seizure,” Jacqueline French, chief medical and innovation officer of the Epilepsy Foundation said in a statement.

Nichol finds the events especially sinister because the attackers used Twitter, which she says is equivalent to a huge public gathering place.

“These attacks are no different than a person carrying a strobe light into a convention of people with epilepsy and seizures, with the intention of inducing seizures and thereby causing significant harm to the participants,’ she said. “The fact that these attacks came during National Epilepsy Awareness Month only highlights their reprehensible nature.

Twitter said it has some tools in place to protect this kind of abuse and are exploring additional options.

“We want people to feel safe on our service,” a spokesperson said in an e-mailed statement to CNN. “We provide people on Twitter with the option of preventing media from autoplaying in their Timelines, as well as prevent any GIFs from appearing when someone searches for “seizure” in GIF search.”

A similar attack in 2016

In 2016, a Maryland man was charged with aggravated assault with a deadly weapon after deliberately tweeting a strobing GIF to a journalist with epilepsy.

The man sent the tweet to journalist Kurt Eichenwald, with the message: “You deserve a seizure for your post,” according to a federal criminal complaint.

Eichenwald said the flashing message immediately triggered a seizure.

After the initial attack, the journalist reported receiving many more similar messages.

“More than 40 ppl sent strobes once they found out they could trigger seizures,” Eichenwald tweeted. “Details of their cases are with the FBI. Stop sending them.”

After hearing the Epilepsy Foundation’s announcement on Monday, Eichenwald tweeted, “When will these idiots figure out we won’t let them try to kill or hurt us anymore?”