The official Luas website has been hacked, with the tram operator being "held to ransom for one Bitcoin".
The hacker has claimed to have breached security and has threatened to publish "all data" if the ransom is not paid in five days.
A message on the website this morning reads;
"You are hacked... some time ago i wrote that you have serious security holes... you didn't reply... the next time someone talks to you, press the reply button... you must pay 1 bitcoin in 5 days... otherwise I will publish all data and send emails to your users."
In a statement this morning, Luas said confirmed that their website was "compromised" and that they have technicians currently working on the issue.
They said they will only be using Twitter for any travel updates in the meantime.
"The Luas website is down at the moment. We will be using this forum only for travel updates should the need arise. We have technicians working on this issue," a spokesperson tweeted.
They later appealed for people to avoid the website as technicians work on the issue.
"Due to an ongoing issue, please do not click onto the Luas website," they wrote.
"We currently have technicians working on the issue. We will be using this forum only for travel updates should the need arise. For any queries, please contact our customer care number on 1850 300 604."
One Bitcoin is worth around €3,382.