The probability of interruption (P_{I}) is the
probability that the security system successfully detects the adversary attacking along the
given pathway so that the response force is able to successfully
engage the adversary and
preventing completion of the intended task.

The probability of interruption is calculated by determining the
combined detection probability before the CDP. This is found
using

Where:

PD,N = the probability of detection
on the N^{th} task

=
the probability that the adversary is not detected until the
N^{th} task