HostsBlocker is a free simple GUI program to block ads, pop-ups, banners, parasites, hijackers, Web bugs by simply using Microsoft Windows HOSTS file. The HOSTS file contains mappings of IP addresses to host names which is loaded into memory at startup, then Windows checks the HOSTS file before it queries any DNS servers, which enables it to override addresses in the DNS.

This prevents access to the listed sites in the HOSTS file by redirecting any connection attempts back to the local machine. Another feature of the HOSTS file is its ability to block other applications from connecting to the Internet. With HostsBlocker, you can add DNS servers you want to block, remove a blocked DNS server, and update the blocked DNS servers online. HostsBlocker includes 12472 blocked DNS servers.