If you're using an article from a news site you must cite where the original article came from with yes, a hyperlink. It's also important that if you're using other peoples content to not publish the entire article on your blog. Post a small portion of the article and near the bottom add: "Continue reading article here"...or something along those lines. You can also rewrite the articles in your own words if you wish. Hope I've answered your question.
How about if the article is rewrited with the same content but looks like totally a different article? Well of course, the content is a general content and not really copyrighted by the author. Shall we link to them back?
If it is rewritten then no link is required, just be sure you don't have consecutive words identical and you will be fine. Of course you could still add a link to the original article near the bottom to be courteous. Also, if you do link back to a certain news site that isn't too popular, then you could possibly contact the owner and exchange links on your blogroll or other advertisements. If you're bringing traffic to his site he will more than likely be fine with it and in exchange for using his content, you get free visitors.
Your best bet is to make sure it's not copyrighted but as a general guideline you usually have to link back. If it is rewritten make sure it's not plagiarized as rewritten material basically the same content with rearranged words.