The Digital Millennium Copyright Act (DMCA) provides a way to stop the piracy. Alas, it is only reactive. It does nothing to prevent piracy, but once it starts you can do something about it. Below I've pasted a take-down letter, courtesy of the wonderful folks at Champagne Books, that you can customize to suit your situation. Reports from authors who've sent the letter show the pirated materials are removed within a few days, sometimes hours. If you'd like more information, you can find several sites devoted to online privacy. Here's one I've used: http://brainz.org/dmca-takedown-101/
It pays to keep a watch for piracy of your books. Set up a Google alert and/or search weekly for your pen name free books. Use as many search engines as you can think of. If you find an unauthorized use, send the letter and let everyone know you've done so. Follow up if you have to; the law is on your side.
Here's the letter:
Re: Copyright Claim
To: the ISP Hosting Company/company name
I am the copyright owner of the eBooks being infringed at:
This letter is official notification under the provisions of Section 512(c) of the Digital Millennium Copyright Act ("DMCA") to effect removal of the above-reported infringements. I request that you immediately issue a cancellation message as specified in RFC 1036 for the specified postings and prevent the infringer, who is identified by its Web address, from posting the infringing material to your servers in the future. Please be advised that law requires you, as a service provider, to "expeditiously remove or disable access to" the infringing material upon receiving this notice. Noncompliance may result in a loss of immunity for liability under the DMCA.
I have a good faith belief that use of the material in the manner complained of here is not authorized by me, the copyright holder, or the law. The information provided here is accurate to the best of my knowledge. I swear under penalty of perjury that I am the copyright holder.
Please send me at the address noted below a prompt response indicating the actions you have taken to resolve this matter.
Email: your email address