How can I block users from accessing Facebook and similar sites on a call centre network?

[Ollie]

[dada]

there is no perfect way to block users from acessing facebook try to use a server gateway here a tutorial
http://www.howtoforge.com/zentyal-as-a-g...fect-setup

[shOrtie]

You do it with your firewall.

[mermeliz]

You can create a host file and place it into the Windows folder. In the file you can add any site address that you want to be blocked by that computer from accessing.
Newer anti-virus programs are trying to get rid of host files so you have to "train" your anti-virus program to leave it alone.

[Heraclius]

You need what's known as a web content filter
To enforce this you Proxy all web connections through this device and your firewall denies Internet access to all other computers
You then configure this to decide what web access is acceptable e.g. block access to gambling sites, social networking sites, etc. allow access to news sites but only during lunch, allow access to IT vendor support sites and so on
Bear in mind any restrictions you make to the Internet needs to be agreed by staff i.e. they need to be made aware of it and accept it as part of their contract. If you're not familiar with that legal requirement you should speak to HR

[gengw2004]

Steps I would recommend:

1. Check your router's firewall features for domain blocking.
2. Install a third party program, ie: WFilter, websense...
3. Try opendns dns filtering solution.