Someone copied my code on Github and claimed it to be his own project.

Last week, a guy copied my source code from Github, even the comments I have written in my source code. Since it wasn't much big of a project, It didn't bother me much (even though I put hours of work into it). In the future, if someone tries to copy my project, how should I proceed? Does having your code on Github mean anyone can copy the code without giving any credit to the owner? I also don't want my projects to be private.