Last December OpenDNS released its tool, called DNSCrypt, for Apple's OS X operating system. The company has now released a technology preview of the same tool for Windows, David Ulevitch, OpenDNS' founder and CEO.

The tool encrypts DNS lookups sent between a person's computer and OpenDNS, which provides a free lookup service. DNS requests are an essential part of the Internet, translating a domain name into an IP address that can be called into a browser.

Most ISPs and other large organizations run their own DNS servers. But OpenDNS runs its own DNS lookup service, and someone can use their service by entering the company's DNS servers into their network settings. The service is free, and OpenDNS claims its service is speedier and has better security.

DNS requests are unencrypted, meaning that an interloper monitoring a person's internet traffic, such as over an unencrypted public Wi-Fi access point at an airport or cafe, could see the requests and compromise a person's privacy.

"Anyone who knows what they're doing can eavesdrop on your Internet activity and see exactly which domains you are resolving, and in many cases, what websites you're visiting," Ulevitch wrote. "Worse, sophisticated attackers can modify responses and redirect you to malicious sites."