Aimed to pin down the people behind the massive breach which exposed personal information of more than 100 million online gamers, Sony hired outside investigators to clean its networks.

A team from privately held Data Forte spearheaded by a former special agent with the U.S. Naval Criminal Investigative Service to team up with the FBI agents remains employed by Sony to do further investigation.

Sony also brought on cyber-security detectives from Guidance Software and consultants from Robert Half International Inc's subsidiary Protiviti to help with the clean-up.

Connecticut Senator Richard Blumenthal asked Sony through a letter to verify the exact number of credit card accounts that may have been compromised. Blumenthal also requested for a detailed summary of their knowledge of the issue.

Blumenthal intends to seek help from U.S. Attorney General Eric Holder to further investigate and check whether Sony's subsequent handling of the breach would make the civilly or criminally accountable.

"I would appreciate a direct and public answer detailing what the company will do in the future to protect its consumers against breaches of their personal and financial information," Blumenthal expressed in his letter.

Law firm Baker & McKenzie Sony was also hired by the electronics giant to help with the investigation.

On Tuesday, a Toronto law firm launched a $1.05 billion recommend class-action suit against Sony for breach of privacy. It also identified a 21-year-old PlayStation user from Mississauga, Ontario as lead plaintiff. McPhadden Samac Tuovi LLP declared in a statement, the damages would cover the fee for credit monitoring services and fraud insurance for two years.