The GAA has warned that the holder of any ticket that becomes known to them as having been bought on the black market could be denied access to Sunday's All-Ireland final.
It comes as some websites continue to offer tickets at hugely inflated prices. The viagogo website yesterday advertised 22 stand tickets, in nine different lots, for a total of €18,809, an average of €855 each. The face value of stand tickets is €80.
Four premium level tickets cost €5,245, of which €684 was described as a booking fee.
The GAA engaged with viagogo via their Twitter account early in the week, asking: "Are you going to help safeguard GAA supporters from overpriced tickets ahead of Sunday's final like DoneDeal and Adverts.ie have?"
Alan Milton, GAA head of media relations, said they later attempted to make direct contact with viagogo but were unsuccessful.
"We're grateful to DoneDeal and Adverts.ie for the manner in which they are helping us clamp down on a clear rip-off," he said.
The GAA acquire some black market tickets every year and track their origin. Croke Park has the facility to cancel those tickets.
"If you buy on websites or through any other black market source, you could find yourself with a very expensive ticket that's useless," said Milton.
Long-term and/or premium ticket holders who are found to have engaged in black marketing risk having their contracts cancelled.
"We can't buy all the tickets advertised on websites but we do get some and act from there. Croke Park's capacity is over 82,000 so it's impossible to keep track of every ticket. But even one ticket on the black market is one too much because it's denying a genuine fan," said Milton.