How can i Secure my Network?

Hello House,

I need a very good idea on how to do these settings:

How to secure my network from virus attack through Router OS,
How to block my client from having access to some websites
Most importantly, am planning to run a commercial proxy, so how can i set my web proxy to hide my client ip address from outside world?

Thanks for helping me out in anticipation.

http://wiki.mikrotik.com/wiki/Firewall