The Irish Times portal site, ireland.com, has disabled a password reminder facility on its free email service, following the unauthorised access of five email accounts.
The action was taken as a precaution to safeguard ireland.com email users when it emerged that an individual had accessed the email accounts on Wednesday evening.
Mr Stephen Finnegan, of Web Ireland magazine, gained access to the email accounts by entering user names and availing of the "password hint" prompt, a facility for users who have forgotten their passwords.
Users who ask for a "password hint" are asked to supply the answer to a question in order to retrieve their passwords. Until Wednesday, users of the ireland.com service were asked to give their mother's maiden name, a pet's name, or the last four digits of their credit card.
"Password hints" are a common feature of many web-based free email services.
Describing the incident as "clever guesswork", the managing director of The Irish Times Electronic Publishing Division, Mr Seamus Conaty, said: "We recognise that password hints offer hackers a way into email and so we have disabled this immediately."
He added that all ireland.com email account holders had been alerted and advised to change their passwords.