Former Tennessee Gov. Bredesen's Senate campaign fears it was hacked

(CNN)Former Tennessee Gov. Phil Bredesen's Senate campaign told the FBI in a letter Thursday that it fears it was hacked.

The revelation comes as intelligence experts predict a widespread threat of cyberattacks on campaigns and election systems from both domestic and foreign hackers.
According to a copy of the letter obtained by CNN, Bredesen's campaign "received multiple emails that appeared to be from the campaign's media buyer" on February 28, which included specific details about a planned media buy and "urged the campaign to wire funds to an international bank account."
    The letter, written by the campaign's counsel Robert Cooper and sent to the FBI's Memphis division, also detailed another email received on the same day which "purport(ed) to be from a principal in the media team that produced the TV commercial, urging transfer of the funds."
    An FBI official confirmed that the Memphis field office received the letter but declined to comment further.
    Following the phishing attempt, the campaign hired a security firm "to determine the extent of any breaches and review security protocols," according to the letter.
    So far, the campaign's cybersecurity team has identified international email hacks originating from the U.K., Nigeria and Ghana, a source familiar with the internal investigation said. According to emails reviewed by CNN, the phishing attempt directed the campaign to wire money to a bank account based in Dubai.
    "Thanks to alert action by campaign management, no funds were diverted," Cooper added. "However, due to the fact that the imposters knew the media buy was imminent, we are concerned that there has been an unauthorized intrusion into the extended campaign organization."
    Bredesen himself appears to have been impersonated by one of the would-be cyber intruders, who emailed his contacts using an address that looked extremely similar to Bredesen's own.
    In an email Thursday, Bredesen warned recipients not to "click a link to view a shared document."
    "Unfortunately, this email is part of an (sic) cyber intrusion into my extended campaign organization," Bredesen wrote, "including an unsuccessful attempt to divert campaign funds to offshore accounts."
    "I'm sorry for the inconvenience; this sort of thing is rapidly becoming one of the unpleasant facts of life," Bredesen added.
    A campaign spokesperson had no additional comment.
    Bredesen, hailed by Democrats as a plum recruit in a red-leaning state, is likely to face off against Republican Rep. Marsha Blackburn in the race to replace retiring Sen. Bob Corker.