Eircom believes it may have established the identity and address of the person who hacked into the company's Internet service, causing disruption to 30,000 customers. However, up to late last night nobody had been arrested as a result of the Garda investigation.
It is understood Eircom managed to track the hacker's movements on its computer systems and was able to establish his identity and his address yesterday. He is believed to be Irish and working from within Ireland, a company source said.
The eircom net site was breached on Wednesday evening with the hacker gaining access to the user name and password of each of the service's estimated 30,000 users. Eircom immediately reported the breach to the Garda Bureau of Fraud Investigation.
If convicted of criminal damage the hacker would face a fine of between £1,000 and £10,000 and/or a prison sentence of between one and 10 years.
Although there was no indication that the hacker had used customers' passwords, Eircom took the precaution of changing them. Customers were advised to ring the usual helpline number to get their new password.
However, despite increasing the number of telephonists, attempts to get through proved fruitless for many. The number was either engaged or rang out.
Eircom said it had attempted to contact as many of its business users as possible and by last night had reached a "high level" of them. A spokeswoman said it would be impossible to say how many of its users were "back up and running" last night.