If you only want to block a handful of sites (I assume
you mean you want to prevent your PC from contacting
these sites) Here's a quick and sloppy method.
Open the file /etc/hosts and add a line for each
site in this format. Let evilsite be the exact hostname of the evil site,
like whatever dot com or www dot whatever dot com
If you want to block more than a few sites, you could consider black hole dns where you run your own name server
that prevents the names from resolving to those sites
you want to block. Malware Prevention through black-hole DNS |