The CEO of Tusla, Bernard Gloster, has said that a member of the public received an "extortion type email" after sensitive information about the individual was accessed.
Speaking on RTÉ's Today with Claire Byrne, Mr Gloster said: "A member of the public received a suspicious email that would have included their own name and certainly at the moment that would have appeared to have been extracted from our system in some way."
He said that the contents of the email included instructions that "this file might be of interest to you, you might want to read this, maybe we can do a deal - those types of robotic emails".
Experts investigating the data breach have said that it was an isolated incident.
Mr Gloster said: "We don't believe at this stage that it's associated with the main cyber attack. It's more of a type of robotic malware that seems to have gotten into our email system.
"All of that appears to be robotic and the only incident we have, but obviously for that person it is very concerning."
The early indication is that it is a "scrape email".
Mr Gloster said: "It takes bits and pieces of different emails. It scrapes them together and it robotically keeps regenerating them together through the system.
"The reality is it is an indication of concern for us, whether it's connected to the main attack or not. We don't believe it is, but we have to remain very vigilant about that.
"In terms of the public interest it doesn't really matter where it's come from, it's a huge matter of concern.
He said that the 14 May cyber attack has had a "crippling" effect on the agency.
Tusla staff are now forced to work with pen and paper as they are locked out of the digital system.
Mr Gloster said: "It really is back to the 1970s, 1980s social care system."
The online referral portal is still down and is not expected to be restored for "about four weeks or more".
Mr Gloster said: "It is a very good system and particularly since mandatory reporting a lot of our mandated reports from healthcare professionals and other professionals, teachers and so on, would use that, so the portal is gone from us for now."
Tusla staff are now taking all referrals over the phone and recording notes with pen and paper.
Mr Gloster said: "The child protection system, which would be the predominant part of our work, is operated by duty intake teams that are dedicated teams that do that work all of the time, so they are taking them by phone.
"It's probably taking a bit longer, because when you're taking a referral by phone, you're obviously talking through all the details and have to write it down with pen and paper."
"Paper presents its own problems in terms of data protection and minding all of that paper."
