A person claiming to be the hacker who accessed Sarah Palin’s private e-mail account has posted online what appears to be first-person account of the simple steps needed to impersonate the Republican vice-presidential candidate and obtain her password online.

The hacker apparently guessed that the Alaska governor had met her husband in high school, and knew Palin’s date of birth and home zip code. Using those details, the hacker tricked Yahoo’s e-mail service into assigning a new password, “popcorn,” for Mrs Palin’s account, according to a chronology of the crime published on the website where the hacking was first revealed.

The FBI and Secret Service have launched a formal investigation into the hack, which occured earlier this week, and the post led bloggers to identify the hacker as the son of a Democratic lawmaker from Tennessee, Mike Kernell.

They claimed to have traced the handle "Rubico" used on the post to an email address owned by Mr Kernell's son, David, a 20-year-old student at the University of Tennessee-Knoxville.

Mr Kernell, who sits in Tennessee's House of Representatives, told local reporters that he was aware of speculation that his son had accessed Mrs Palin's personal email, but said he could not say whether the authorities had contacted him.

Yahoo declined to comment on the investigation, citing Palin’s privacy and the sensitivity of such investigations.

The self-confessed hacker, whose gender was unclear, described himself or herself as a "lurker" and claimed to have found nothing incriminating in Ms Palin's e-mails, "nothing that would derail her campaign as I had hoped."

The person added: "All I saw was personal stuff, some clerical stuff from when she was governor…. And pictures of her family”.

Palin’s hacker was challenged to guess where Alaska’s governor met her husband, Todd. Palin herself recounted in her speech at the Republican National Convention that the pair began dating two decades ago in high school in Wasilla, a town near Anchorage where she later became mayor.

“I found out later though (sic) more research that they met at high school, so I did variations of that, high, high school, eventually hit on ’Wasilla high’,” the person wrote.

The hacker wrote that the prank was cut short because of panic over the possibility the FBI might investigate, the hacker wrote.

If the details of the break-in into the account are genuine, it fits with speculation by computer security experts who said Yahoo’s “forgot-my-password” service almost certainly was exploited.

The service allows customers to retrieve or change their password if they can verify their identity by confirming personal information such as birthdate, zip code (postcode) and the answer to a “secret question,” such as a childhood pet’s name or school mascot.

Hacking into Mrs Palin’s private account was significant as she sometimes uses the e-mail to conduct official business. Previously disclosed e-mails indicate her administration embraced Yahoo accounts as an alternative to government e-mail, which could possibly be released to the public under Alaskan law.

At the time of the hacking, critics of Palin’s administration were poring over official e-mails they had obtained from the governor’s office looking for evidence of improper political activity.

The McCain campaign issued a statement describing the hacking as an invasion of Palin’s privacy.

Mr Kernell said that he had not been contacted by the authorities regarding the case and was not sure whether they had been in touch with David. "I can't say. That doesn't mean he has or hasn't (been contacted by investigators)."

He said he had talked to his son today, but that he talks to his son regularly. He declined further comment.

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