Host Flash™ is software written for Linux based computer operating systems. Host Flash™ makes it easy for Linux computer admins and users to block access to websites.

Host Flash™ builds a list of hostnames to which access requests must be denied. This has the effect of blocking access to undesirable websites; which means data and content like adverts, malicious scripts, tracking beacons, adult media or other items can be blocked.

The easy answer is that a hostname is a domain name or website address.

The host name is the name for a host server that is normally stated in words that human’s can easily recall and refer to.

The technical answer is that a hostname, also spelled ‘host name’, is the name of host server where a data resource can be reached. That resource could be a website accessed through the Internet or through an intranet, or it could be one of multiple hosts stationed on the same computer that requests data from them.

For example,

• google is a hostname in google.com
• maps is a hostname in maps.google.com
• com. is a hostname of its own. Notice the period (full stop) at the end.

The hostname is independent of the access protocol use to reach it such as HTTP, HTTPS, SVN or FTP, for example.

Servers, like web servers, are associated with an Internet Protocol (IP) address. A single computer could host many servers and so could be associated with many hostnames.

Domain Name Servers (DNS servers) keep index of IP addresses and the hostnames that can be reached through each computer associated with an IP address. A computer’s local hosts file is used to bypass indexes held by remote DNS servers.

Back to the simple answer. Think of a hostname as being a website domain name.

The hosts file is a computer’s local index of the IP address where a hostname can be reached.

When the Internet was in its infancy, users of networked computers connected via private intranets or the public Internet needed to keep a local record of the IP address used by a hostname. This record was kept in a network connected computer’s own local hosts file.

Local hosts files needed to be regularly updated to add new IP address to hostname mappings as new hosts became available and to edit details of IP address changes.

The hosts file grew in size and became difficult to manage with the growth of the number of hosts added to the Internet. Remote Domain Name Servers (DNS servers) were created to replace the need for locally managed hosts files.

A computer checks the locally held hosts file when a it is tasked to connect with a host. A computer will consult with a remote DNS server to find the IP address of a requested host when the requested host name is not found in the local hosts file.

A hosts file can be used to bypass remote DNS server indexes and to redirect host name requests to alternate IP addresses. For example,

• requests to reach google.com can be redirected to an IP address used by bing.com, or
• requests to reach facebook.com can be redirected back to the computer that was tasked to request facebook.com, i.e. back to the localhost, which would mean the request would not leave the computer.

In Summary

A hosts file is an index of IP address to hostname pairs (mappings). Those mappings look similar to,

127.0.0.1 google.com
127.0.0.1 bing.com
127.0.0.1 adserver.com

The hosts file is read before a DNS server is requested. The hosts file takes precedence over the DNS server index.

Domain Name Servers (DNS servers) keep index of IP addresses and the hostnames that can be reached through each computer associated with an IP address.

Host Flash™ uses a combination of up to 23 hostname blacklists compiled by reputable sources and a locally held user configured list of hostnames to block.

The remotely compiled blocklists are maintained at, and downloaded from,

• hosts-file.net
• winhelp2002.mvps.org
• rlwpx.free.fr
• hostsfile.org
• and others

The locally held user configurable blocklist is called blocklist.txt and is stored in the Host Flash™ program directory.