The City of Westmount confirmed Monday evening that it was hit with a cyberattack, which has caused a computer outage and disabled the city's email servers.

"The Information Technology Department is working with a leading external cybersecurity firm to determine the extent of the attack and how to re-establish our systems as quickly and efficiently as possible. The City’s website is unaffected," read a statement on the city's website.

The cyberattack was first reported by La Presse, which said the hacker group Lockbit had gained access to 14 terabytes of data and demanded a ransom to be paid, otherwise the files would be published in two weeks.

The City of Westmount did not respond to multiple requests for comment from CTV News. At a council meeting early Monday evening, officials addressed the attack but did not confirm it was a ransomware style of cyberattack. They asked members of the public to communicate with the city via phone or in person at a service location.

"Cyberattacks are unfortunately becoming more and more prevalent and sophisticated in our society and, despite all the measures we put in place, public administrations are not completely immune to this sad reality. I want to reassure all Westmounters that our teams are working seriously and diligently to remedy this situation, and we will keep residents informed," said Westmount Mayor Christina M. Smith in a written statement.

A cybersecurity expert said the hacker group has exaggerated the size and scope of stolen data in the past, but may have started using smarter tactics.

Jacques Sauve, an analyst who helps businesses mitigate risks of cyberattacks, said in previous cases hackers would encrypt files after infiltrating a network and then demand a ransom.

"But then the customers got wise and they started doing good, solid backups. So when their data was encrypted, they would just restore and go, 'I'm not going to pay.' So the bad guys decided on a new tactic: let's steal the data first, then encrypt. So now we're looking at double extortion and this is most likely what's going to happen here," Sauve said.

"I'm sure the town of Westmount has all their backups, but can they withstand having 14 terabytes of data — citizen data, private information — published on the dark web and that's where they'll have to decide whether to pay the ransom or not."

The City of Westmount said citizens can find the service directory on its website as IT teams try to resolve the hack.

With files from CTV News' Kelly Greig