Hackers sent emails with malicious software attached to Hillary Clinton's private email account at least five times in August 2011, the Associated Press reported late Wednesday.
But it is not clear that Clinton's server was ever exposed by the "phishing" attempts.
"We have no evidence to suggest she replied to this email nor that she opened the attachment," a Clinton campaign official told NBC News. "As we have said before, there is no evidence that the system was ever breached. All these emails show is that, like millions of other Americans, she received spam."
Clinton's account received five emails disguised as traffic tickets on the evening of August 3, 2011. The messages, all titled "Uniform Traffic Ticket," appeared to be from the New York State Department of Motor Vehicles and prompted the recipient to print out an "enclosed ticket" for a speeding offense.
"Description of violation: Speed over 55 zone," the message read. "To plead, print out the enclosed ticket and send it to Town Hall, Chatam Court Hall, PO Box 117."
Security experts told the AP that the malicious software would have allowed hackers to take control of the computer if a recipient using the account had opened the attachments, although it is not clear that Clinton did so.
The AP writes that, if infected, the computers would have transmitted information "to at least three server computers overseas, including one in Russia."
But, as the AP notes, that doesn't necessarily mean Russian intelligence or citizens were responsible.