Encrypting your data is the best way to protect yourself against mass surveillance. By using a VPN, you prevent your ISP from collecting data about your online activity (and any government agencies that are copying that data). If your ISP does not have information about what you do online, they cannot share it with SIGINT agencies in Five Eyes countries. However, if you use a VPN that is based in a Five Eyes country, any logs they keep on your online activity can be shared with all the SIGINT agencies in the UKUSA agreement. Proton VPN is based in Switzerland, which is not part of the Five, Nine, or Fourteen Eyes agreements. The same can be said of encrypting your emails. By encrypting your emails, you ensure that no one else can access the contents of your messages. (Note: If you email someone who is not using an encrypted email service, the contents of your emails will not be protected by zero-access encryption on their side.) You can also use privacy-focused browsers and encrypted messengers to further protect yourself from mass surveillance.