"International gangs" participating in online video challenges have caused €2million in damage to Irish trains over the past two years, the National Transport Authority has said.
The gangs are involved in a common worldwide trend that defaces trains around the globe.
The NTA's public transport chief Tim Gaston explained to the Dublin City Joint Policing Committee on Tuesday: "A particular problem that has emerged in the last 18 months to two years is international graffiti gangs are coming to Ireland with the specific purpose of getting their social media hits."
