The best way to prevent illegal copies circulating around the internet is to offer your content legally in as many stores as possible, for a price that is similar to other books in the same genre.
PublishDrive does not specifically add any protection to the books, but all of our store partners do. The most common method stores use to protect your books is DRM (Digital Rights Management).
The so-called hard DRM (used by stores like Amazon, Google Play, Apple Books, Scribd, etc.) prevents copying your content by not giving the actual EPUB file to the buyer and allowing them to read only in their own reading app. Other ebook stores use soft DRM, which usually means watermarking technologies: ebooks can be copied, but all data of the buyer will be hidden within the book, in a way that the buyer will not find it.
Please note that none of these technologies are perfect and online piracy is evolving every day. If you do end up finding your book illegally on a site, you can initiate a DMCA takedown. Read more about how to do it here.
Before starting the DMCA process, make sure that the book is actually there and downloadable. There are numerous phishing sites whose only purpose is to get the personal data of unsuspecting internet users. Sometimes they will use books to lure users and they promise they will be able to download the book by entering their personal and credit card details. They do not in fact have the book file on these sites and the user will not get anything even if they hand their data over. If you find your book on a site like this, you can rest assured that it is not actually being distributed, just used as a lure to deceive someone who is looking for it.