Was Russia really behind the DNC hack, or was it the work of a freelance teenage hacker confined to his bed by morbid obesity? Republican nominee Donald Trump raised the question at tonight's presidential debate, as the candidates approached the topic of cybersecurity.

After Secretary Clinton criticized Trump for seeming to call for additional cyberattacks by Russia earlier this year, Trump responded by calling the attribution of the DNC hack into question.

"I don't think anybody knows it was Russia that broke into the DNC," Trump said. "It could be Russia. It could also be China. It could also be someone sitting on their bed that weighs 400 pounds."

Attribution is a notoriously tricky business, and while many experts have privately expressed a belief that Russia is responsible for the emails stolen from the DNC, Trump is right that no official attribution has been made. It could indeed be China, or a bed-ridden hacker without state affiliation.

Both candidates agreed on the seriousness of digital attacks, and the challenge they present the federal government over the coming presidential term. "Cyberwarfare will be one of the biggest challenges facing the next president," said Clinton.

"Cyber is very tough" Trump concluded. "I have a son. He is 10 years old. He has computers. He is so good with these computers, it's unbelievable."