For this you have several options as different companies offer their own versions. These can be either entirely free or some programs can be paid. It is important to check what is available for you with both programs so therefore compare and contrast their abilities.
One thing that you need to be aware of is how often it is updated. New spyware appears constantly so you need one that can deal with the very latest threats. You need to set it up so it is updating by itself automatically so you do not have to worry about trying to remember.
It is always a good idea to look at what computer professionals say about these programs. Of course the companies behind them are going to say how wonderful they are so looking at reviews can give you the best idea away from the sales jargon. Read more than one review though to get you a better picture including reviews from people who already use the program.
You are looking for effectiveness and how easy it was to set it up as your main points to consider. Ideally you just want it working away in the background not slowing your computer up a great deal and yet you knowing it is protecting you constantly.
So to conclude you should consider if you want the free or paid versions. Often the free can be adequate but lack things that the paid version has. Check how often they get updated and keep it updated to catch the latest threats. Also check computer professionals for reviews to get honest answers about how good or bad they are. Remember it is effectiveness and ease of use that are the key to this kind of program. I am glad that all the spyware on my computer are all gone now all thanks to high quality anti-adware software which you can find out more about at my website link below.