A range of Government websites were shut down for up to 12 hours in the latest in a series of cyber attacks.
The distributed denial of service (DDoS) targeted the Department of Justice, the Courts Service, the Oireachtas and the Central Statistics Office among others.
Some disruption lasted as little as one hour while other sites were shut overnight up until about midday on Friday.
The attacks follows the shut down of the lottery on Wednesday, operated by Premier Lotteries Ireland, with ticket sellers also taken offline as they prepared for one of the biggest draws of the year.
Some of the gov.ie sites remained shut overnight with most coming back online after midday.
The DDoS type of cyber attack is where a website is overwhelmed by huge numbers of requests and web traffic to a server at one time forcing the system to crash.
While it is not normally used to allow hackers to steal personal information it has been used in the past by online activists such as Anonymous.
A video, purportedly from the group, was posted online over a year ago in which threats were made over the imposition of water charges.
Other sites to have been hit by DDoS attacks this week include boards.ie.
The Department of Public Expenditure and Reform, which oversees some of the Government sites, said the source of the cyber attack could not be traced.
“These attacks have resulted in periodic disruption that has resulted in a number of Government websites becoming unavailable to the public,” a spokeswoman said.
“We have implemented our contingency plans which are designed to minimise this disruption. As with all DDoS attacks it is not possible to identify the exact source of the attack.”
