Facebook, WhatsApp and Instagram were investigated by the Data Protection Commission last year.
They were among the 15 technology companies that control their compliance with GDPR examined.
The annual report of the Data Protection Commission shows that more than 4,700 valid violations were reported between May and December 2018.
That is a 70% increase in the number of data violations in Ireland since the introduction of new GDPR laws.
Over 2,800 claims were made to the office, 56% more than in the previous year.
Graham Doyle, of the Data Protection Commission, said that all of these investigations are under way.
"There are six different companies," he said.
"There are nine of these queries that have been opened that are complaints-based queries, and then we have had six other queries that we open for our own will.
"Some of them are a result of notifications of individual violations."