You can use NxFilter. You can read a review of it here.
It is remarkable really. It used to be that a web filter needed a complex setup and lots of time by IT to configure it. This software actually is relatively easy to set up, although you probably will want an IT person or consultant to help you.
Once this is set up, it allows you to control what happens on your network. More than just filtering websites you may not want to see, it protects you from suspicious activity that hackers use. Web filtering is required for everyone now because of all the garbage on the web. Going on the web without a filter is like walking into a forest buck naked and a large target painted on your back. I wouldn’t advise it unless you like being attacked.
What I like about this is that you don’t have to switch over your DNS infrastructure from whomever your provider is. I like that as a DNS filter you can easily turn it on or off without affecting client machines. I also like that you don’t need any client software. Client software is always a pain to deal with and complicates and slows things. It is neat too that it is a free product. It is a clever combination of features that should be more popular.
I used to work in businesses that had complex setups for web filtering and it caused all kinds of issues. It was slow, it introduced one point of failure and just generally wasn’t something you wanted. It also was very limited in what it could do, and didn’t protect against the ways smart people could get around it. What is neat about NxFilter is that it stops that behavior and for 99% of people, it will stop smart users.
Is this right for an enterprise? Maybe if money is an issue. Another option is iBoss which I am also investigating but has large costs and time. Only you know what is best for your company.