Is it possible for spywares/ virus not to be detected by network monitoring tool ( for eg TCPView) if they are sending information/files over internet ?
This really comes down to where you are running the network monitoring and how low level the malware is.
Most malware that you see (from my experience) is not low-level enough to re-write networking stacks to where local monitoring tools would not see the traffic. This could happen though, so there is always a change of the traffic blindly passing through. You are getting more into root-kits and things like that, not you everyday malware when this happens.
If you run the network monitoring on the gateway/router, you are going to see the traffic from the machine, now matter how low-level the malware is. This will show you all traffic coming from a host if it is on the gateway, no matter how the traffic is disguised.