I took the advice of the selected answer to this question and used OpenDNS on my Ubuntu computer but I wanted to share more information to be helpful to others.
What is OpenDNS, and how to get OpenDNS?
OpenDNS is a free DNS service that can not only speed up your internet but also provide you options like...
The bottom line is OpenDNS servers have a huge collection IP addresses of millions of web pages. When you look for a website, it immediately finds the corresponding IP address and hence gets it to load faster. It's intuitive and literally takes less than 10 minutes to set up (no software installation required)
To utilize all its features, all you need to do is sign-up with them here. Basic OpenDNS is suitable for your household devices is free of cost. (For business solutions there is a nominal annual fee)
Once you have signed up, you’ll get a confirmation link in your mailbox. Click on the link and it will redirect you to dashboard settings on the main website.
It will automatically detect your IP address. Click on Add this network button given below your IP address All you need to now is to follow the Instructions provided on the website and add these IP addresses to your router.
Preferred DNS server: 18.104.22.168
Alternate DNS server: 22.214.171.124
That's it! You're done
By default, nothing is blocked. You have FULL control to select one of 3 pre-sets 1: Low 2: Moderate or 3: High filtering levels
Example: If you choose “Low” filtering level then all the porn sites will be blocked . You increase the filter level to apply more restrictions. There is also a custom filtering levels that allows you to be specific or tweak one of the pre-sets.
You can block or allow any domain of your choice by entering the domain name. It also gives you the ability to add an extra layer of security as it provides malware and botnet protection as well as phishing protection. You may also block internal IP addresses.
Important note of caution:
I have been using OpenDNS for a couple of weeks now and I created a Bookmark in Firefox. Stupidly I clicked on "Remember my Password" which means anybody can click on the bookmark get into OpenDNS and make changes. I have since rectified.