Sony Pictures’ top brass have voiced their anger over last week’s “brazen” cyberattack that wreaked havoc on the studio’s network. Cyber thieves, they warn, now have their hands on “a large amount” of the company’s confidential data, according to an email obtained by TheWrap website.

In a joint email reportedly sent to the company’s staff, Sony Pictures Entertainment CEO Michael Lynton and Co-Chairman Amy Pascal said they are “deeply saddened” by the hack. The executives describe the mysterious attack as a “concerted effort to do damage to our company, undermine our morale, and discourage us.”

“It is now apparent that a large amount of confidential Sony Pictures Entertainment data has been stolen by the cyber attackers, including personnel information and business documents,” wrote Lynton and Pascal, in the email.

“This is the result of a brazen attack on our company, our employees and our business partners,” the executives added. “This theft of Sony materials and the release of employee and other information are malicious criminal acts, and we are working closely with law enforcement.”

The FBI has launched a probe into the attack. The agency also sent out an “FBI alert” to companies in the entertainment sector, describing the characteristics of the so-called “wiper malware” used in the attack.

The finger of suspicion has already pointed at North Korea over the attack. Earlier this week a source familiar with the FBI alert told Fox News that the highly destructive malware was written in Korean, further fueling suspicions that Pyongyang launched the cyber attack.

However, the Korean-written malware also may have been an attempt to confuse investigators about its origin, according to the source.

Sony Pictures’ forthcoming film “The Interview,” starring Seth Rogen and James Franco as journalists enlisted to assassinate dictator Kim Jong-un, has outraged North Korea.

In June North Korea submitted a letter of complaint to the U.N., urging the U.S. to prevent the film’s release. U.N. officials released the letter on Wednesday.

“To allow the production and distribution of such a film on the assassination of an incumbent Head of a sovereign State should be regarded as the most undisguised sponsoring of terrorism as well as an act of war,” wrote North Korea's U.N. ambassador, in the email.

On Nov. 24 a hacking group called Guardians of Peace, or GOP, took over Sony Pictures’ corporate network and vowed to release sensitive corporate data if certain demands were not met. Variety reports that screener copies of at least five Sony movies were downloaded freely online following the hack. In a further twist, a spreadsheet appeared on a text sharing site Monday purportedly showing the salaries of top Sony Pictures executives.

Sony Pictures has not yet responded to a request for comment on this story from FoxNews.com. The company’s letter to staff, however, provides some hints as to the scale of the attack.

“While we are not yet sure of the full scope of information that the attackers have or might release, we unfortunately have to ask you to assume that information about you in the possession of the company might be in their possession,” it said. “While we would hope that common decency might prevent disclosure, we of course cannot assume that.”

Sony Pictures is providing identity protection services to all its employees via Austin, Tex.-based AllClear ID, according to the letter.

Culver City, Calif.-based Sony Pictures is a subsidiary of Japanese tech and media giant Sony.

Follow James Rogers on Twitter @jamesjrogers