Apparatus and method for interfering with an unauthorized device attempting to acquire user identification information at a cash dispensing automated banking machine. The apparatus includes an emitter for emitting radiation at one or more frequencies to interfere with actual or suspected radiation transmitted from an unauthorized device in a proximity of the banking machine. The radiation may be substantially continually emitted or emitted responsive to a user supplying input to the machine. The radiation may be emitted over a plurality of frequencies within a frequency range associated with unauthorized devices. Additionally, the machine may include a sensing device for monitoring the nature and quality of unauthorized radiation.