From the WSJ:

The Federal Bureau of Investigation said Monday it was investigating a cyberattack into former President Donald Trump’s campaign that stole internal communications.

The announcement is the first sign that the U.S. government has launched a probe into a suspected Iranian hack-and-leak operation amid mounting fears of Tehran’s desire to interfere in the U.S. presidential election. 

It is unclear what could result from the FBI probe, and the bureau declined to comment further. The U.S. government hasn’t said publicly whether Iran was involved, as the Trump campaign has alleged.

Iran has quickly emerged as the chief election security concern within the U.S. government. Just last month, U.S. intelligence officials told media reporters that Russia was the “pre-eminent threat” to the November vote and viewed Iran as a lesser concern seeking solely to generate discord.

But weeks later, they shared that their assessment on Iran had changed: Tehran wasn’t just hoping to spread chaos, they said, but aiming to harm Trump’s candidacy, as it haphazardly sought to do four years ago. Iran was also attempting to directly engage Americans in its influence operations and even provide funding to support Gaza protests on college campuses, officials said, while relying on “vast webs of online personas and propaganda mills to spread disinformation.”