I follow a lovely artist both here and over on Furaffinity called vera.

She made a really good journal I'd like to share with you folks:
http://www.furaffinity.net/journal/8381943

It really captured my views of potential character theft and what to do about it. I certainly agree with this way of handling the situation. Just remember to always be calm, cool and collected. It can be difficult, but if the situation gets hairy and you remain calm and logical in your actions, you are sure to come out in the right!