"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."
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Speaking on RTE Radio 1, Irish Rail spokeswoman Jane Creegan explained that the gangs "tag a train" and upload a "challenge video" on social media for others to catch the train at a station further down the route and deface it.
She described the issue as a "new phenomenon" for Irish Rail.
"Graffiti has unfortunately has always been an issue for us but this particular style of graffiti is something that has only emerged in the past 18 months," she said.
"It's an international phenomenon that began in New York and Berlin in the 1970's and 1980's where people would graffiti or target a particular train and then go to another location to get that same train.
"Obviously the onset of video and social media has made a difference to that as well."
Ms Creegan said she would describe the graffiti as "criminal damage", not art.
"I would see it and the organisation would see it more as criminal damage more than art because when this happens to trains, they have to be taken out of service to be cleaned and there's a significant cost and can cause a service impact as well.
"We do have live monitors and CCTV in a lot of stations so we can see where this is happening.
"We engage very closely with gardai and thankfully we have had a number of arrests recently."
Ms Creegan said that Irish Rail's information suggests that the culprits are mostly non-Irish residents coming here from different parts of Europe and America to engage in the antisocial behaviour.
She urged anyone who witnesses such behaviour to contact Irish Rail by texting the word "TRAIN" followed by your report to 5144 or to contact gardai.
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