It's in P2P networks (e.g. BitTorrent), where people share content. While you download, you offer what you already have downloaded and that's associated with yo

It's in P2P networks (e.g. BitTorrent), where people share content. While you download, you offer what you already have downloaded and that's associated with your IP. And that's their attack vector: you're distributing copyrighted content without a license. After that file hosters (e.g. Rapidshare) became popular, where only one person is uploading and the downloaders are hard to identify and even harder to sue.