Bukkit

This plugin needs to have a time delay option between actions, if there was an option that admins could set so that EC objects like cubes and everything else can only be used say once every 3 seconds it would help avoid major exploits this like one. One exploit that will crash the server every time, is a cube that cuts off its own redstone power supply, it will get stuck in an infinite loop of turning on and off, as fast as the server is able to process it until the server overloads and crashes. It usually only takes 2-3 seconds to bring down the server when this happens. An example of a server crashing cube is below. For the Electric craft sign you can use

line1=Blank
line2=[EC]
line3=Cube
line4=20 20 20 20
(20 20 20 20 will ensure a crash but is not needed, all you have to do is create a continuous loop)

S=Sign
W=RedstoneWire
B=Any block
C=Cube
R=Cube Source Block
X=Air
P=Power
View as if looking from the side

XXCCCXXX
PWCCCXXX
BBWXRXX
BBBWSXX
BBBBBBBB
That or make your plugin detect when it starts a continuous loop and break the connection/operation.