Cyber-attacks against the US by Iranian hackers have eased noticeably since the countries' landmark nuclear weapons accord, National Security Agency director Michael Rogers has said.

Speaking at a House Intelligence Committee hearing on Thursday, the Wall Street Journal [paywall] reported him saying there had been “significant Iranian activity” related to cyber-attacks against US financial firms a couple of years ago.

However, since nuclear negotiations with Iran picked up speed in 2014, “we saw less activity directed directly against us", he said.

In April, the countries came to a landmark agreement over Iran's nuclear capabilities, preventing Iran from acquiring a nuclear weapon and ensuring "that Iran's nuclear program will be exclusively peaceful going forward".

Of course, when it comes to cyber-attacks the US has a much better track record than Iran.

In 2011 the Stuxnet worm crippled Iranian nuclear enrichment facilities, repeatedly attacking five industrial plants inside Iran over a 10-month period.

The stealth of the attack was so effective that Iran didn't even seem to be aware that the damage was the result of an attack until the media started reporting the story.

The US and Israel have never formally admitted to being behind the worm, having refused to discuss it on record.

However, researchers have speculated the countries were behind the malware, intended to disrupt Iran's nuclear ambitions. ®