If your smartphone or tablet uses iOS 10 or Android 6 with Duo, then you need to upgrade to newer versions of the operating software by July 28. After that date, Duo will not work securely with iOS 10 or Android 6.

Duo Security announced the end of Duo support for iOS 10 and Android 6 on May 1. “Focusing on newer [operating systems] allows Duo to continue building helpful and secure features,” the company said. “We encourage users to upgrade to the latest OS versions to ensure devices are not vulnerable to security issues and to provide … the best Duo Mobile experience.”

Starting this summer, you’ll see greater use of Duo multi-factor authentication at UC Davis. And as use grows, the damage caused by phishing will shrink.

Duo is a security app. It works by asking you for two “factors” when you sign in to an account protected by Duo: your usual password, plus a temporary code created by Duo, typically sent via the Duo app to your smartphone. (There are alternatives if you can’t use a smartphone—more below.)