Null route the msn servers ip on your site. here's how:
high tech solution:
1- Completly close msn and disconnect from irc, kazaa, or whatever network intensive activities
2- Download
Ethereal on your computer
3- Set it to capture packets on your network card. Start the capture
4- Start up msn and connect. let it sit for a few seconds, then disconnect
5- Stop the capture
6- Examine the captured packets (there's a filter built-in that will filter out anything but msn packets, i believe)
7- Find the ip or host of the msn servers where msn messenger is connecting to
8- Open up your HOSTS file (in windows xp, it should be hidden in c:\windows\system32\drivers\etc\ , its an hidden file, so enable the display of those files in explorer)
It should look like this (watch out, fucked up formatting ahead)
See the 127.0.0.1 Localhost part? Well, just start a new line, and add this:
123.123.123.123 being the ip that you got from analysing the msn packets. If analysing the packets gave you a host name, use
this to resolve it and get the ip.
Save, and reboot. Now the next time that your sister will try to get on msn, msn messenger will get rerouted to localhost (your computer!) and just give an error message saying it couldnt find the server / couldnt connect.
If she's really addicted, she will use the online msn clone that use java. You could use ethereal again (filter out the http connections) and then find out where she's connecting from. Re-route the connection using the same trick.
Tell me if it worked.