Speedhack operate by sending commands to the server faster than regular, this results in an acceleration of the speed of the player.
sXe Injected blocks this hack easily by counting the number of commands that the client is sending, if the commands count becomes larger than the regular count, then his future commands are ignored, it has the effect of the player gets stuck.
Anti-Speedhack is a server-side feature, a cheat operates in the player's computer, this means that there is no cheat that can override this protection.
Anti-WallHack
Anti-SpeedHack
Anti-NoFlash
Anti-SoundHack