The FBI and US Secret Service have opened criminal inquiries into the hacking of a private email account used by CIA Director John Brennan and his family, the FBI said on Thursday.
The investigations followed the posting on social media earlier this week by the hackers of data stolen from an AOL account. Intelligence officials said the account was used by Brennan and his family, but was not used to transmit or store government secrets.
"The FBI is investigating this matter jointly with the US Secret Service. As this is an ongoing investigation, we declined further comment," said a spokeswoman at Federal Bureau of Investigation headquarters in Washington.
The case marked another instance of hacking involving the US government or government officials, although it appeared to be of a much smaller and more primitive character than previous attacks, such as the massive breach of Office of Personnel Management computers in June.
"The hacking of the Brennan family account is a crime and the Brennan family is the victim. The private electronic holdings of the Brennan family were plundered with malicious intent and are now being distributed across the web," the CIA said in a statement on Wednesday.
"This attack is something that could happen to anyone and should be condemned, not promoted. There is no indication that any (of) the documents released thus far are classified," the spy agency added.
Material from the Brennan account was published by a hacker who called himself "Cracka" and said he was working with a group called CWA, or Crackas With Attitude. It included email contact addresses, some of which were out of date, and the Social Security numbers and personal information of US intelligence officials.
On Wednesday, the WikiLeaks website posted data from the Brennan cache including a draft version of Standard Form 86, which government employees must fill out when applying for a security clearance. Brennan's form included personal information on himself, acquaintances and close family members.
WikiLeaks also posted what appeared to be unclassified documents on Iran and CIA interrogation practices, some of which were publicly circulated years ago.
Wired Magazine published an interview this week in which the purported hacker described how he and two associates conned telecommunications company Verizon into giving them information which enabled them to hack into Brennan's AOL account.