Freeware developer Sordum has released DNS Lock, a free tool which prevents malware (or anything else) changing your IPv4 DNS addresses.

Launch the program’s single executable and it prompts you to enter your primary and secondary DNS IP’s.

DNS Lock offers you a choice of Open DNS and Google DNS Servers, too, although it only displays the raw IP addresses without identifying what they are.

Once you’ve chosen or entered your details, the program applies them to your system and installs a Windows service to keep them safe.

We tried changing our settings via the usual Windows route (TCP/IP properties), and it wasn’t possible. There were no error messages and everything appeared to work, but when we reopened the dialog, the protected settings were back.

Setup is easy and there’s no system tray icon or other runtime interface to get in your way

If you find the program gets in your way, launching it and choosing “Uninstall Service” removes the protection and returns your system to normal.

Dns Lock can also be controlled from the standard Services applet (Run > Services.msc), although this didn’t always work as we expected. Stopping the service allowed manual changes to your IP addresses, but restarting it didn’t restore the protected values until we rebooted.

Despite that, Dns Lock is a handy tool which keeps your DNS settings safe with the absolute minimum of hassle and resource usage.

DNS Lock is a free tool for Windows XP and later.