The company that runs Luas says 3,226 people who signed up to the Luas newsletter may have had their records compromised after its website was hacked.
However, they say no financial information has been compromised.
Transdev has taken its site offline, after a message appeared on its homepage this morning demanding one Bitcoin, which is worth over €3,000.
Luas say they will write to those people affected within the next 24 hours informing them of the potential breach.
The site is being analysed to identify how the attack occurred and technicians are working to restore the service for customers.
An Irish cybersecurity firm has said that the ransom demand on the Luas website is likely to be "the first of many in 2019".
Cybersecurity firm Smarttech 247 is urging businesses and the public to ensure their computers have the protection they need against an increasing number of ransomware attacks.
It comes after a message on the Luas website appeared today claiming it has been hacked, with the hackers demanding payment of one Bitcoin.
Transdev have said the website could be down for the day.
The apparent hack of the Luas website matches a trend that has already been detected by experts, Smarttech 247 said.
CEO of cybersecurity firm Smarttech 247, Ronan Murphy said: “Although it’s only three days into the new year Smarttech247 team have already seen a sharp rise in ransomware attacks.
"These are primarily spreading via email where they appear to be a Microsoft document (word, excel). The Ransomware will attack any server or computer which does not have adequate protection and this includes web servers that host websites and applications.”
Earlier: Luas website taken offline after hacker demands a Bitcoin
Luas operators are asking people not to visit its website after it was hacked overnight.
A team of engineers have taken the website offline completely as they look into the issue.
Anyone that visited the Luas website this morning was greeted with a message stating it had been hacked.
The apparent attacker said that it had written to the tram operators some time ago, claiming the website had "serious security holes".
The hacker was threatening to publish all data if Transdev did not pay one Bitcoin, or around €3,400, within the next five days.
Operators have tweeted urging people not to visit the website as it has been taken offline, adding that they have a number of technicians working on the issue.
Due to an ongoing issue, please do not click onto the Luas website. 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.— Luas (@Luas) January 3, 2019
Luas has said it will update customers via twitter, Facebook, AA Roadwatch and the media if there are any changes to services today and has apologised for the inconvenience.