A Hillary Clinton aide says he made a fatal typo that led to John Podesta's email hack

A Hillary Clinton aide said he made a typo that led to the email hack which plagued Democratic presidential nominee Hillary Clinton's campaign through its final months.

Clinton's campaign chairman John Podesta fell victim to a cyberattack earlier this year when hackers breached his email account through a phishing message that purported to be from Gmail, telling him to change his password immediately because a third party had attempted to log into his account.

Before Podesta took action, an aide that had access to his account saw the email purporting to be from Google and forwarded it to a computer technician asking if it was legitimate.

Charles Delavan, a Clinton campaign aide, replied with a fatal typo.

"This is a legitimate email," Delavan replied. "John needs to change his password immediately."

Delavan told The New York Times in a story published Tuesday that he had meant to type that it was an "illegitimate" email, but accidentally typed "legitimate" instead.

Thousands of Podesta's emails were leaked in the final months of the campaign. US officials have accused Russian hackers of interfering in the presidential election to help former Republican nominee and now President-elect Donald Trump.