Yair Ramati headed a branch of the ministry developing Israel's missile defence system. He served in the position for four years.
The ministry announced Ramati's dismissal late yesterday. It gave no further details, but defence officials said he had kept sensitive information on his personal computer. The officials spoke on condition of anonymity because they were not authorised to talk to the media.
Israel is considered a world leader in missile-defence technology. It is developing a multilayered system meant to defend against everything from long-range guided missile attacks from Iran to crude rockets fired from Lebanon and the Gaza Strip.