Apple said in an email — as noted by AppleInsider that all app developers will be required to use the company’s two-factor authentication protocol to protect their Apple IDs.
Here’s the bulk of the letter: “In an effort to keep your account more secure, two-factor authentication will be required to sign in to your Apple Developer account and Certificates, Identifiers & Profiles starting February 27, 2019. This extra layer of security for your Apple ID helps ensure that you’re the only person who can access your account. If you haven’t already enabled two-factor authentication for your Apple ID, please learn more and update your security settings.”
The email links to a support page covering two-factor authentication for Apple ID, as well as a contact form directed to Apple Developer Relations.