Will Editing HOSTS file in Ubuntu Improve my Network Security?

You should use 127.0.0.1, the so-called loopback address. Unlike 0.0.0.0, it is a valid IPv4 address.

While it is true that this mitigates some tracking issues, this does not improve security per se.

There are a gazillion sites that track you, and you can't keep up editing your hosts file. To prevent tracking, you'd better use plugins like AdblockPlus and NoScript that auto-update the list of sites to block.

Also note that security is a process, not some setting or configuration.

To strengthen your security, you also need to consider

• setting up a firewall
• physical access to your machine
• lots of other things that would be out-of scope here.