CHICAGO (WLS) -- Lurie Children's Hospital confirmed their network was "accessed by a known criminal threat actor" during a press conference on Thursday.
Thursday marked the ninth day of Lurie Children's working offline without phones, email and other communications, due to a cyberattack.
Hospital officials did not provide information about who the criminal actor could be. Internal and external cyber experts are working with the FBI to find the source.
"As soon as the matters occurred we implemented our emergency preparedness plans, including downtime procedures throughout the organization," Chief Nursing Officer Brian Stahulak said.
Thursday was the first time the hospital publicly acknowledged the cyberattack. Cybersecurity experts said the hospital could have nine days as part of a safety strategy.
"Imagine if you're at war, you can't expose your situation to your enemy," cybersecurity expert and CMIT Solutions President Jeremy Treister said. "You might want to express some ideas of what you're doing, some strategy, but it's dangerous to go into detail about every move you're going to make."
Why would hackers want to disrupt a children's hospital?
"It could be ransom," Treister explained. "It could be for political gain. Maybe they just want to make themselves known out there that they are the experts. Because there is a whole business out there of hiring hackers to get into your systems".
Cybersecurity experts said depending on the size and complexity of the network, it can take several weeks to recover from a cyberattack.
A call center has been established to address needs including non-urgent patient requests, care questions, information regarding scheduled patient appointments, and patient prescription refill requests.
The Lurie Children's call center can be reached by calling 1-800-543-7362, and is operational Monday to Friday from 8 a.m. to 8 p.m., Saturday from 8 a.m. to 5 p.m., and Sunday from 8 a.m. to noon.
Patients should visit luriechildrens.org for the most up to date information about their operations.
See Thursday's full press conference in the player below.