The cyberattack on Sony was so bad, employees there were forced to resort to an ancient technology -- the BlackBerry.

Executives also used the tried-and-true tactic for relaying messages: a phone tree.

CEO Michael Lynton told the Wall Street Journal Tuesday that it took him more than a day to fully understand the severity of the attack.

It was crippling.

Hackers stole troves of data, leaking movies and internal documents exposing private company memos, along with employees' salaries, Social Security numbers and health information.

Plus, the company's entire computer system was down during the week of Thanksgiving. Here's some of the ways workers coped, a Sony spokesman told CNNMoney:

Execs set up a phone tree, so they could update each other about the hack. One person would relay the message to the next person on the "tree."

Employees used personal cellphones, Gmail accounts and notepads.

Paychecks were cut manually.

Old BlackBerrys, which operate on a different server, were revived to send emails.

The FBI has presented evidence that North Korea was behind the hack. It came just before Sony was about to release "The Interview," a comedy about a plot to kill North Korean leader Kim Jong-Un.

But some security experts hackers and people familiar with Sony's computer networks aren't so sure it was North Korea that pulled it off.