The CAO website containing offers of college places for students crashed this morning because of an attack from an unknown, malicious source.
The CAO website was later restored and is now accessible.
Tens of thousands of CAO applicants were due to log on this morning to view and accept or reject offers made to them.
But shortly after the service went up at 6am, the CAO server was attacked. It is believed to be a denial of service attack, which is the most common kind of attack.
It caused the CAO server to be overwhelmed by tens of thousands of bogus requests.
Dealing with all these bogus requests means it had got no time for valid ones.
The CAO said the issue was resolved at 1pm by technical staff.
It reassured applicants that they would receive their offers by post and could accept by post too.
The points requirements for entry to many third-level courses have increased this year as a result of increased competition for places.
The first round of offers for places from the Central Applications Office were available on the CAO website before the cyber attack this morning.
3,000 additional applications were made this year bringing the number to more than 77,500.
The biggest course in the country, arts in University College Dublin, is up five points to 365.
Some other arts courses remain the same or are down.
Many science and maths related courses have seen a steep rise in entry requirements.
UCD's science degree programme is up by 50 points to 435.
Points for science at both University College Cork and NUI Galway are up.
Mathematics at Trinity College Dublin is up by 70 points to 485 and by 40 points to 545 at NUI Maynooth.
Points for many computer science courses have also increased.
There have been some dramatic points drops too.
Architecture is down across the board, most dramatically at the University of Limerick, where it has fallen by 60 points to 400.
The points for medicine and many nursing courses have risen.
Applicants who are accepting a round one offer have until 30 August to accept.
Round two offers will be made on 2 September.