UPDATE, 3 PM: Sony chief Michael Lynton also issued the following internal memo to employees:

Over the last week, some of you have asked about the strength of our information security systems and how this attack could have happened. There is much we cannot say about our security protocols for obvious reasons, but we wanted to share with you a note we received today from Kevin Mandia, the founder of the expert cybersecurity firm that is investigating the cyber-attack on us. The investigation is ongoing, but Mr. Mandia’s note is helpful in understanding the nature of what we are dealing with. Full text below.

We also want to thank you once again for your resilience and resourcefulness in carrying out our critical day-to-day activities under incredibly stressful circumstances.  As a result of your efforts, we have made great progress moving our business forward, and we will continue to do so.

Dear Michael,

As our team continues to aid Sony Pictures’ response to the recent cyber-attack against your employees and operations, I wanted to take a moment to provide you with some initial thoughts on the situation.

This attack is unprecedented in nature. The malware was undetectable by industry standard antivirus software and was damaging and unique enough to cause the FBI to release a flash alert to warn other organizations of this critical threat.

In fact, the scope of this attack differs from any we have responded to in the past, as its purpose was to both destroy property and
release confidential information to the public. The bottom line is that this was an unparalleled and well planned crime, carried out by an organized group, for which neither SPE nor other companies could have been fully prepared.

We are aggressively responding to this incident and we will continue to coordinate closely with your staff as new facts emerge from our investigation.

Sincerely,

Kevin Mandia

Previous, 2:41 PM: Sony chiefs Michael Lynton and Amy Pascal are working to stop the widespread cyber-attack that has impacted the company.  Lynton recently sent out the following email to Sony employees:

We are understand that some our employees recently received an email containing malicious and threatening contents from an unknown sender. We immediately notified the FBI of the email and they have teams working on this issue.

First and foremost, if you happen to receive a suspicious email DO NOT respond to these emails or click on any links. Not only are these criminals using scare tactics, they may also be attempting to further infect the SPE IT network. Once again, we cannot overemphasize our appreciation to all of you for your commitment and resolve. Together we will move past this incident and continue the extraordinary work you do every day.