LED lamps very low power consumption and is usually a large operating voltage range, it is often 85-260V, so they glow from even the slightest leakage current.
Common causes of leaks:
1. The switch is illuminated in the chain constantly under tension, it is not enough to light a conventional or halogen bulb, but is enough to feed the led or energosberegenie
2. The switch breaks the circuit - at one time the rules prescribed by the scheme where the switch breaks the zero bus, and not phase, allegedly for security that the current is less than hit, this scheme is found widespread in the Khrushchev and some of their followers. it is applicable for incandescent lamps, because fluorescent and diode again getting a leak through the concrete construction of the building, parallelnye lines, etc.
3. There are sometimes other less common factors