Someone had also defecated on the back steps of the council office at one point.
On police recommendation, the Ruapehu District Council began switching off the wifi after-hours on April 20 in an attempt to reduce vandalism and "other anti-social behaviour".
"In addition to the vandalism, council staff in Raetihi have also had increased levels of abuse recently, which is of significant concern," Ruapehu District Council policy and planning group manager Pauline Welch said.
"The council is also looking into installing security cameras which have been very effective in Taumaranui and Ohakune at helping to curb these types of issues and in identifying offenders."
The free wifi has been offered for about three or four years but it is unclear why vandalism has only recently become a big issue, a council spokesman said.
He said the mayor told council members at a meeting recently it was believed gang members were coming up from Whanganui and trying to recruit young people "so that's adding to the issues".
Ms Welch said it was "unfortunate" the steps needed to be taken, because it affected the whole community as well as visitors and tourists.
"Ultimately this is a community issue and it will require a concerted whole of community response to resolve," she said.