They're protected by copyright automatically when you write them (assuming you're not just rewriting someone else's material, in which case they own the copyright to the original, and are the only people allowed to authorize or make derivative works). As for making people obey the copyright laws, unfortunately in most cases you have to take action after the fact. But adding a copyright notice stating all rights are reserved is a start at least.
Be more specific about what you mean by 'protect'. The copyright notice might deter some people, but not all. If you're trying to keep people from copy/pasting your article, I think there's a Java script somewhere that disables copying any highlighted text in a frame.
You could just plug your website address into copyscape (www.copyscape.com). I believe that part of the application is free.
Go to www.google.com/alerts. Set up an alert for your byline. Set up optimized alerts for a sentence from your articles. If you don't use quotation marks, you'll probably get tons of irrelevant alerts.
This is not a good idea to protect your online work. A simple view source of the page will allow a user to copy the exact lines.
That kind of javascript also royally pisses off a lot of regular readers (not a smart idea). There are legitimate cases where someone may want to copy a quote and blog about your post for instance (good for your site). Scripts to stop that (like those sad little things that don't let you right-click) deter that kind of word-of-mouth marketing. Personally, when I go to a site that disables right-clicks or something similar, I almost never go back.
I hate that right click script. I often forget where I put a file and then I can't find it with properties and have to scan all the code for it.
Just go to copyscape.com and enter your web address. I believe that part is for free. Copy Scape also provides free "do not copy" warnings that you can place on your site.
So copyscape runs a search and looks for content equal to yours on other sites. Does it only recognise text verbatim? Or similar?
I want to say (well, I guess I am saying) it recognizes strings of 3 or more words that are verbatim, but I'm not sure where I'm getting that...it might be in the Copyscape FAQ.