Question: Is it possible to deny or prevent or obstruct a network scan on the network where your computer is connected to?

Answer: 
If you don't want your pc to be scanned for open ports or available services, you can use a firewall that closes/stealths the necessary ports. Beware, certain ports wil always be open to be able to communicate with the network.
First, go to Start Menu->Run window. Type `cmd`. In the command prompt enter the following commands:

```
Net config server /hidden:yes

```

This command will hide you from the Network neighborhood but your shared folders can still be access.

Note: in Windows Vista, you need to open the command Prompt as Administrator: Start Menu > type `cmd` > `Ctrl`+`Shift`+`Enter` and hit Continue.

or else you’ll get this message:

```
System error 5 has occurred.

Access is denied.

```

So how about my IP address? what if they have an ip-scanner, still they can find me?

They can find you by using an ipscanner. The solution for this problem is by using a Firewall. Upgrade to Windows XP Service Pack 2, there is a free inbound protection firewall. For Windows Vista users, there is an inbound and outbound firewall protection by default.

To check if your computer is hidden in the network neighborhood type this in the command prompt:

```
Net config server

Server Name \\MyPc 
Server Comment

Software version Windows Vista (TM) Ultimate 
Server is active on 
NetbiosSmb (MyPC) 
NetBT_Tcpip_{4365E532-AF25-4C8E-C31E-5D3BG50F7043} (MyPC)

Server hidden Yes 
Maximum Logged On Users 10 
Maximum open files per session 16384

Idle session time (min) 15 
The command completed successfully.

```

How to Show your Computer Again inside the Network Neighborhood

```
Net config server /hidden:no

```

Enjoy!

Note: *It only works for windows xp sp2 and up use as admin and open cmd as admin if you can still be found update your pc and install a good firewall like Zone Alarm-Firewall.*