unbelievable situation

hi to all,
I have a big trouble with my yun!
I can't understsnd why when I'm really close, few centimeters from the board, it close the circuit, exactly the same situation such as I'm closing with button (closing the circuit with cable connection from pin 7 to 5v, turn on led with button example)
do you think could be the static current or something else?
many thanks your collaboration

What exactly is your circuit? It sounds like your connection is pulling the line high, and you're looking for the input to read high. In such a case, you MUST have a pull-down resistor to prevent the input from floating.

I'm going to go out on a limb and guess that you don't have a pull-down resistor. A floating input is very susceptible to electrical noise. Your body acts like an antenna and picks up 60 / 50 Hz line frequency and other electrical noise very easily. When you get close to the Yun, this gets radiated to the floating input, causing it to randomly turn on.