Thank you so much!
Agreed Linux is a fortress and nothing can be installed without permission. Since I don't know linux commands, I am not going to use sudo command for anything without knowing what it might do. I shall use only synaptic manager to install any application. I have installed script blocker to firefox. I shall be careful about the websites I visit. By the way, isn't there a phising filter in firefox (like in IE)?
You DO need a firewall. But not an antivirus.
This is what I found on use of a firewall @ *www.funnestra.org/ubuntu/hardy/#ufw
Although the Linux kernel has a built-in firewall, it is turned off by default since Ubuntu installs in such a way that no ports are listened to by any program or process. Since nothing is listening to any of the ports, there is no need for a firewall. However, once you enable something like file or printer sharing, remote desktop, etc., processes will start to listen to some of the ports for external connections. You should therefore enable the firewall and create rules to restrict access of the appropriate ports to the IP addresses of the desired set of machines.
Regular updates, firefox and evolution mail use internet connection, so I probably won't need a firewall, right?
Antivirus is not required, (I am convinced) but IF anyone still needs one, Avast has it.
*www.avast.com/eng/download-avast-for-linux-edition.html
And if you have any more basic questions please refer these before asking
*www.funnestra.org/ubuntu/hardy/
*ubuntuguide.org/wiki/Ubuntu:Hardy
Thank you so much, I was looking for something like this.