Russia-linked hackers tried at least five times to trick Hillary Clinton into infecting her computer systems while she was US secretary of state, newly-released emails show.
Mrs Clinton received the virus-riddled e-mails, disguised as speeding tickets from New York, over four hours early on the morning of August 3, 2011.
The emails instructed recipients to print the attached tickets - and opening them would have allowed hackers to take over control of a victim's computer.
Security researchers who analysed the malicious software in September 2011 said that infected computers would transmit information from victims to at least three server computers overseas, including one in Russia.
Nick Merrill, a spokesman for Mrs Clinton's Democratic presidential campaign, said: "We have no evidence to suggest she replied to this e-mail or that she opened the attachment. As we have said before, there is no evidence that the system was ever breached. All these e-mails show is that, like millions of other Americans, she received spam."
The messages show hackers had Mrs Clinton's e-mail address, which was not public, and sent her a fake traffic ticket from New York state, where she lives. Most commercial anti-virus software at the time would have detected the software and blocked it.
The phishing attempts highlight the risk of Mrs Clinton's unsecure e-mail being pried open by foreign intelligence agencies, even if others also received the virus concealed as a speeding ticket from Chatham, New York.
The e-mail misspelled the name of the city, came from a supposed New York City government account and contained a "Ticket.zip" file.
Mrs Clinton has faced increasing questions over whether her unusual e-mail set-up amounted to a proper form of secrecy protection and records retention. The e-mails themselves - many redacted heavily before public release - have provided no shocking disclosures so far and Mrs Clinton has insisted the server was secure.