Try to disable flights in Survival Mode (Hi Mr_Anderson)

mods/PLAYER/mcl_anticheat/init.lua

@@ -0,0 +1,128 @@
+local flights_kick_threshold = 10
+
+local after                 = minetest.after
+local get_connected_players = minetest.get_connected_players
+local get_node              = minetest.get_node
+local get_player_by_name    = minetest.get_player_by_name
+local is_creative_enabled   = minetest.is_creative_enabled
+local kick_player           = minetest.kick_player
+local pos_to_string         = minetest.pos_to_string
+
+local ceil  = math.ceil
+local floor = math.floor
+
+local window_size = 10
+local detection_interval = 1.7
+local step_seconds = detection_interval / window_size
+local joined_players = {}
+
+local function update_player(player_object)
+	if not player_object then return end
+	local name = player_object:get_player_name()
+	if not name then return end
+
+	local pos = player_object:get_pos()
+	local x, y, z = floor(pos.x), floor(pos.y-0.1), floor(pos.z)
+
+	if mcl_playerplus.elytra then
+		local elytra = mcl_playerplus.elytra[player_object]
+		if elytra and elytra.active then
+			return
+		end
+	end
+
+	local air = get_node({x = x    , y = y    , z = z    }).name == "air"
+		and get_node({x = x    , y = y    , z = z + 1}).name == "air"
+		and get_node({x = x    , y = y + 1, z = z    }).name == "air"
+		and get_node({x = x    , y = y + 1, z = z + 1}).name == "air"
+		and get_node({x = x + 1, y = y    , z = z    }).name == "air"
+		and get_node({x = x + 1, y = y    , z = z + 1}).name == "air"
+		and get_node({x = x + 1, y = y + 1, z = z    }).name == "air"
+		and get_node({x = x + 1, y = y + 1, z = z + 1}).name == "air"
+
+	local player_data = {
+		pos = pos,
+		velocity = player_object:get_velocity(),
+		air = air
+	}
+
+	if joined_players[name] then
+		local window_offset = (joined_players[name].window_offset + 1) % window_size
+		joined_players[name].window_offset = window_offset
+		joined_players[name][window_offset] = player_data
+	else
+		joined_players[name] = {
+			window_offset = 0,
+			[0] = player_data,
+		}
+	end
+end
+
+local function check_player(name)
+	if is_creative_enabled(name) then return end
+	local data = joined_players[name]
+	if not data then return end
+	if not data[0] then return end
+
+	local always_air = true
+	local falling = data[0].velocity.y < 0
+	for i = 0, window_size - 1 do
+		local derivative = data[i]
+		local not_enough_data = not derivative
+		if not_enough_data then
+			return
+		end
+		always_air = always_air and derivative.air
+		falling = falling or derivative.velocity.y < 0
+	end
+	if always_air and not falling then
+		-- fly detected
+		if not data.flights then
+			data.flights = 1
+		else
+			data.flights = data.flights + 1
+			if data.flights >= flights_kick_threshold then
+				kick_player(name, "flights")
+			end
+		end
+		local obj_player = minetest.get_player_by_name(name)
+		if not obj_player then
+			kick_player(name, "flights")
+		end
+		local velocity = obj_player:get_velocity()
+		local pos = obj_player:get_pos()
+		local x, y, z = floor(pos.x), floor(pos.y), floor(pos.z)
+		while (     get_node({x = x    , y = y, z = z    }).name == "air"
+			and get_node({x = x    , y = y, z = z + 1}).name == "air"
+			and get_node({x = x + 1, y = y, z = z    }).name == "air"
+			and get_node({x = x + 1, y = y, z = z + 1}).name == "air"
+		) do
+			y = y - 1
+		end
+		obj_player:set_velocity({x = velocity.x, y = -10, z = velocity.z})
+		obj_player:set_pos({x = x, y = y + 0.5, z = z})
+	end
+end
+
+local function remove_player(player_object)
+	if not player_object then return end
+	local name = player_object:get_player_name()
+	if not name then return end
+	minetest.after(step_seconds, function()
+		joined_players[name] = nil
+	end)
+end
+
+local function step()
+	for _, player in pairs(get_connected_players()) do
+		update_player(player)
+		check_player(player:get_player_name())
+	end
+	after(step_seconds, step)
+end
+
+minetest.register_on_joinplayer(update_player)
+
+minetest.register_on_leaveplayer(remove_player)
+
+after(step_seconds, step)

mods/PLAYER/mcl_anticheat/mod.conf

@@ -0,0 +1,3 @@
+name = mcl_anticheat
+author = kay27
+depends = mcl_playerplus