We are an internet based company who hires independent contractors to complete work for us. They are paid per job. One contractor was dismissed due to issues with her work. She again signed up, this time under another name, and completed more work for us. We discovered who she was and removed her again. She has since done this three more times. Each time we have figured out who she is, but not before she has completed work for us. Each time she signs up using a different name, address, phone number, or email address with different banking information. It is getting harder to track. So, she is signing up fraudulently, and chances are, since she has completed work under five different names, that she is not claiming all of her earnings with the government. It is very time consuming having to investigate issues with her, and is bordering on harrassment. Are there any legal avenues we can take to keep her away from our business?