Pirate Bay is generally not illegal, since it does not sell its own content or advertisements. It is just a forum to share peer-to-peer. Therefore, you can use the website without doubt if you are in a country where the website has not been banned. And you can still access it through the numerous pirate bay proxy sites, even if it is blocked in your region. There are mirror pages that have separate domain names and IP addresses and the same material that is accessible on the original site. However, any mirror website cannot be declared secure, authentic. While most of them are secure, others sell adware and other malware.