I discovered a url linking to my site this morning and was shocked to find someone registered my same domain name under a ".ru" extension. This person is mirroring the content on my site! He is only feeding in the homepage though, all the links in the navigation link back to my ".com" site. He is also linking the images from my site to his .ru.
My question is can this hurt our ranking with Google? Should I be concerned? What can I do about it?
Is it possible this can hurt you - yes. Is it likely this will hurt you - no.
If two pages have duplicate content, Google tries to figure out who the original is and then filters out the copy. Worst case scenario is the site that stole your content is able to trick Google into thinking they are the original and you are the copy to be removed from the search engine. That is not easy to do.
I would not be very concerned about this. I would monitor it and make sure the other site is not doing anything else. If I noticed they were doing some heavy link building I would become much more concerned.
Here are some actions you can take: A) You can email the offending webmaster. If this is accidental and they are nice they will respect your copyright and remove it. I doubt this is the situation.
B) Contact the hosting company of the offending website. Many hosting companies want to avoid legal issues and will remove copyrighted material from their servers. Since this is an international case, it is less likely.
C) File a DMCA request. DMCA is the legal process for copyright holders to have their content removed from the internet. Improperly filing a DMCA request can open you up to lawsuits. Be careful when dealing with DMCA requests.