Do not depend on it alone. If it finds such a request, the interceptor generally pops up and asks you if you want to allow the request to continue. There is, however, no reliable way to intercept direct branches into low level code or to intercept direct input and output instructions done by the virus itself.
Some viruses even manage to disable the monitoring program itself.
It is important to realize that monitoring is a risky technique. Summary Interceptors are useful for some simple logic bombs and Trojans. It would be unwise to depend entirely upon behavior monitors as they are easily bypassed.