On Wednesday, Wikileaks published several screen shots of Yahoo e-mail messages, e-mail addresses of Palin family members and associates, and other data that hackers claim to have obtained from Palin's private Yahoo account.
One e-mail message appears to be from Alaska Lieutenant Governor Sean Parnell, complaining to Palin about an interview by Alaska radio show host Dan Fagan. "Arghhh! He is so inconsistent and purposefully misleading," Palin apparently writes in response.
A hacking group known as Anonymous gained access to Palin's Yahoo account late Tuesday night and sent the information to Wikileaks, which acts as an anonymous clearinghouse for leaked documents.
"Governor Palin has come under criticism for using private email accounts to conduct government business and in the process avoid transparency laws," Wikileaks wrote in a note accompanying the material. "The list of correspondence, together with the account name, appears to re-enforce the criticism."
Late Wednesday, the McCain-Palin campaign confirmed the hack. "This is a shocking invasion of the Governor's privacy and a violation of law," the campaign said in a statement. "The matter has been turned over to the appropriate authorities and we hope that anyone in possession of these emails will destroy them."
Thursday, the Secret Service and FBI confirmed they have begun investigating the hack.
Palin's e-mail practices had been discussed in the press in the days before the hack, after Alaska activist Andree McLeod had sought to obtain more than 1,000 e-mail messages that Palin had withheld following a public records request.
Last week, the Washington Post reported that Palin routinely handled governor's business from the address firstname.lastname@example.org. However, that is not the account that Anonymous hacked. Screen shots of the Yahoo pages posted to Wikileaks show that they had access to a email@example.com address.
Palin may have been using several Yahoo addresses in order to keep e-mail from friends and family separate from her other mail, said Adam O'Donnell, director of emerging technologies with e-mail security vendor Cloudmark.
There are several ways that attackers could have gained access to this account, O'Donnell said. They could have simply guessed her password, or had enough of her personal information to trick Yahoo into resetting the password. A more sophisticated attacker might have somehow installed key-logging software on Palin's computer or obtained the information though a phishing attack, he said.
Yahoo declined to comment on the matter, saying that it does not comment on specific user accounts for privacy reasons.
Made up of a loosely knit group of volunteer hackers, Anonymous gained notoriety earlier this year for launching an online attack against the Church of Scientology's Web site.
Palin is the governor of Alaska. She was named John McCain's vice-presidential running mate on Aug. 29.