Shearer has introduced stringent new regulations with increased fines for offenders as he attempts to foster a recovery on and off the pitch, with midfielder Joey Barton suspended until further notice by the club for a breach of discipline.
That has apparently not gone down well with some of the players he inherited from Joe Kinnear and Kevin Keegan before him, but 34-year-old Harper, who like Shearer played under Sir Bobby Robson's regime, insists it has been a positive change.
Harper told NUFC TV: "Players respond to discipline, it's needed.
"At times in the past, it maybe wasn't what it should have been here.
"But he [Shearer] has tightened it up and players respond to it, and that can only be a good thing."