Copy protection is provided for the now-unprotected computer monitor port of a computer 100 in two ways: (i) delaying synchronizing signals by a time variable amount and (ii) generating pulses during non-active video. Delay of the synchronizing signal is performed by selecting a fixed offset 203 and selecting either the fixed offset of the pseudorandom delay to be sent to a variable delay generator 260, which delays the horizontal synchronizing signal 201 by the selected amount. This new delayed horizontal synchronizing signal 202 is encoded by the CRT Controller 244 and is then sent to the computer monitor 164, which uses the delayed synchronizing signal 202 as encoded to produce its display in conjunction with a data signal. Thus, if these signals 202, 268 are intercepted by a VGA to TV converter 122, the converter 122 (or any downstream device) is unable to lock onto the correct frequency in order to reproduce the image properly. Horizontal pulse bars 218 may also be generated to render a signal unfit for taping purposes. The horizontal pulse bars 218 are generated to replace the portion of the video signal containing no picture information after vertical picture contraction has occurred. The amplitude of the input signal 212 is reduced, and the amplitude of the pulse bars 218 is increased to be greater than the amplitude of the input signal 212. The horizontal pulse bars 218 are then combined with the attenuated signal 214. When a VHS recorder 116 detects the amplitude of the modified signal, it lowers the amount of gain added to the signal because of the high amplitude of the added pulses. As the data content of the signal is at a much lower amplitude than the added pulses due to the attenuation, the viewable picture after taping is extremely dim and of poor quality.