FishingExploits - dniym/IllegalStack GitHub Wiki
Fishing exploit protection is divided into two different protections, one involves exploiting a game mechanic that allows a player to either hold down the mouse button with a heavy object, or use a macro program to have the client constantly send left clicks while fishing. This type of fishing is easily detectable and will not give any false positives.
Auto Clicker Fishing Protection (More Info)
The second method involves using a modified client that can mimic real fishing, this protection may give some false positives, however it DOES warn the player that they have triggered the detection before any action is taken.