[bob1029]

DSSS is sort of both security and obscurity at the same time. The very act of spreading your spectrum out via a secret key also has the effect of reducing the amplitude of your transmission, ideally below the noise floor. A receiver on the other side wouldn't see anything except noise unless they had the same key.

[adrian_b]

The same is true for any other method of spread spectrum modulation, e.g. for FHSS (frequency-hopping spread spectrum) or for ultra-wideband pulses.

The detection of weak signals requires long integration times, which remove from the output any spread spectrum signal present in the input, unless you know and apply before the integration the correct scrambling or frequency-hopping sequence.