Blocking Advertising

Internet advertising is one of the biggest risks to your security and privacy so it’s important to block it if you value these things, some might argue it’s wrong to block advertising but when it puts you and your computer at risk there is no other option.

Internet advertising can be blocked by three main methods:

  • Hosts file
  • DNS filter
  • Browser plugins

Most people these days use browser plugins such as AdBlock, Adblock Plus or my personal preference and recommendation uBlock Origin, these in general do a very good job at blocking advertising but don’t work outside the web browser, they can also be used to remove unwanted elements from a web page giving you a cleaner browsing experience.

Hosts File

The hosts file is a little more complicated to explain, when you go to a website such as http://www.google.com your computer needs to lookup the domain name to obtain the internet address such as 216.58.198.110, this is done by contacting a DNS server which is typically provided by your ISP, however in the early days of the internet there was no DNS servers, instead it looked in a hosts file which manually maps domain names to ip addresses, for example:

216.58.198.110 http://www.google.com

The hosts file typically has priority over the DNS server so you can use it to override the domain name resolution, this is usually done by redirecting the domain to the local loopback address which is 127.0.0.1 or 0.0.0.0, this effectivly blocks the domain.

On windows the hosts file can be found at C:\Windows\System32\drivers\etc\hosts
On Linux and most other UNIX based systems it can be found at /etc/hosts

To make things easier you can find hosts files online that already block the majority of advertising providers and other unsafe domains, I’m currently using Steven Black’s hosts file which is compiled from several different reliable sources.

This applies to all applications on your system but I still recommend it be combined with a browser plugin for maximum coverage.

DNS Filter

Rather than at the hosts file the blocking can also be done at the DNS server level, you can either do this by setting up your own DNS server or by using a public DNS service such as OpenDNS.

Personally I don’t use these public services out of privacy concerns but if you want a very simple method that needs no maintenence this might be for you, one big advantage of this is that it works on devices where you cannot typically access the hosts file.

If you have a Raspberry Pi laying around consider installing pi-hole on it for a super simple hardware DNS server.

Advanced Blocking

Sometimes you may run in to an advert that is not blocked by any of your installed methods, in a web browser it’s easy to add new blocking rules but outside you may need to find which domain it’s coming from.

This is easily done by tools such as Process Explorer or Wireshark which can show all HTTP connections, with a little effort this is usually able to locate the offending domain, for cases where the connection is made directly by IP address you can block it using a firewall such as TinyWall or Windows Firewall.