Australian Manufacturing Workers Union Tasmanian secretary John Short said about 9.30pm, the factory’s computer system went down, believed to be the target of malicious software affecting companies worldwide.

The software reportedly locks computer files and calls for a $300 ransom to be paid through Bitcoin.

Mr Short said he believed other Cadbury plants across Australia had also been impacted.

“The factory runs with computers, so there’s been no production since and they’re just trying to work out how to fix it,” he said.

“The information is a bit patchy at the moment because I don’t think they know what they need to do so we’re just going to have to wait and see.

“Sometimes there’s power outages or sometimes big machines close down but I’ve never seen anything like this.” 

TasICT chief executive William Kestin said businesses and individuals needed to take action to keep their information safe, not just on computers, but on mobile phones and tablets as well.

“These types of hacks are very dangerous and the thing that most people don’t realise is just how often they actually happen,” he said.

“Most businesses are fairly unprepared when it comes to the cyber security crimes that have really expanded.

“About 93 per cent of the time, it only takes a few minutes for these cyber criminals to get into and access your information, and 95 per cent of those are financially-geared.” 

Mondelez International, the owner of Cadbury, said it was working to address the issues and contain any further exposure to its network.

“Our teams are working offline in an effort to maintain business continuity with our customers and consumers around the world,” the company said in a statement.

“At this time, we do not know when our systems will be restored but we appreciate everyone’s patience.”