The Domain Name System is an essential component of the functionality of the Internet. DNS translates domain names into IP addresses. Most Internet users are using their Internet Service Provider’s DNS server. Though it's convenient to use the ISP's DNS, its not the safest.
Alternatively you can use Public DNS. Popular ones are Open DNS and Google DNS. Another good alternative is Norton DNS which act as a first layer of defense against unsafe, fraudulent, phishing and infected Web sites. Norton DNS is free for home users.
Norton DNS doesn't guarantee a full protection against viruses and malwares, but it does prevent users from browsing infected websites.
Another feature is that it acts as a Content filter preventing users from Web sites with undesirable content.
It also gives option of choosing protection policy for instance if you would only like to block malware, phishing and scam sites or all Non-family friendly sites (including mature content, drugs, gambling and violence).
For detailed instructions on how to setup Norton DNS you can visit their website