Anti Kb Mod 1.8.9 -

if (packet instanceof S12PacketEntityVelocity) 
  S12PacketEntityVelocity v = (S12PacketEntityVelocity) packet;
  if (v.getEntityID() == mc.thePlayer.getEntityId()) 
    if (mode == CANCEL) cancelPacket();
    if (mode == SCALE) v.setMotionX(v.getMotionX()*scale); // require reflection

if (entity == mc.thePlayer) 
  entity.motionX *= scale;
  entity.motionY *= scale;
  entity.motionZ *= scale;

Even if you don't get banned immediately, a "Staff Ban" is common. A moderator watching you in /vanish (invisible mode) will see you taking zero knockback from a punch bow or TNT. They don't need a program to ban you; human observation is enough.

The Minecraft community distinguishes between quality-of-life mods (OptiFine, Schematica, Replay Mod) and blatant cheats (Anti KB, KillAura, Fly). anti kb mod 1.8.9