I know two applications used to connect over internet to play cs...
1. Hamachi(which I have not used yet;))
TeamViewer is a simple and fast solution for remote control, desktop sharing and file transfer that works behind any firewall and NAT proxy.
STEPS TO CONNECT THROUGH TeamViewer
STEP1 : Download the teamviewer download from here
STEP2 : Open the application
STEP3 : From the above window, we can see our id is 127 256 125 and password is 6666.Now choose one of the players who will become server for the VPN connection. Ask the id of the server and type the same on right hand side textbox labeled id in the CREATE SESSION form , select the VPN radio box and click the button Connect to partner
(in this window, the id of VPN SERVER is 126 903 822)
(ask the password of the server VPN)
STEP4 : Once the connection is established, the following window will appear
your ip address is 126.96.36.199
server ip address is 188.8.131.52
NOTE : 1. ROLE OF TEAMVIEWER IS OVER,MINIMIZE IT(DONT CLOSE IT)
2.VPN SERVER IS NOT SPECIAL, A PRIVATE CONNECTION HAS BEEN
ESTABLISHED AND EACH PEER HAS ITS OWN IP ADDRESS.
3. ANY OF THE PEER CAN CREATE SERVER IN COUNTER STRIKE.
STEP5: All the peers open the same game either CONDITION ZERO(yellow icon) or
COUNTER STRIKE1.6(white icon)
SIXTH STEP IS FOLLOWED BY THE PEER WHO WILL BECOME SERVER FOR COUNTER STRIKE,ANY AMONG THE PEERS CAN BECOME SERVER
STEP6:In the following window,COUNTER STRIKE1.6(white icon) is opened
Click on New Game,select the map.
Do the game settings(optional)
Click the Start button...so the server established
SEVENTH STEP IS FOLLOWED BY THE PEERS WHO WILL JOIN THE SERVER ESTABLISHED ABOVE.
THE PEER WHO HAS ESTABLISHED THE SERVER FOR COUNTER STRIKE SHOULD TELL HIS IP ADDRESS TO ALL THE PEERS
STEP7 : Click on Find Servers
Click on the tab Favorites
Click on the button Add Server
Type the ip address of the peer who has established the server for the game.
Refresh the page twice or thrice.....the server name should be visible in the list
Select the required server from the list and click on the Connect button
(here the server is Freaky_ss)
enjoy the game:)