What your are allowed to do on the internet is a complex issue. There are no simple answers. It depends partly on which country you are physically located and partly on where you go in cyberspace. There are ethical and legal considerations, as well as policy considerations from the level of who owns the computer providing the internet service all the way to the national and international level. To complicate matters further, the internet is really a global network of networks, and each network may have its own policies, rules, and regulations.
Some internet providers provide rules and standards of conduct they expect each user to follow.
Other internet providers may have only vague guidelines or none at all. However even the internet providers that do have detailed rules may not always tell you everything that you need to know. The Naval Postgraduate School has developed clear policy for proper internet use. You should familiarize youself with these guidelines. There may be other legal issues that are equally important, however these are the ones I am familiar with.