When you're asked what your favorite app is, you're probably not going to name a notes app. Be honest with yourself, though: Your note-taking app is the app that's always there for you, whether you're making a grocery list, you're a celebrity who needs to make an apology, or you've changed your work-computer password for the zillionth time and you need a handy place to store it. It's your secret best friend, but your notes app could be giving away all your secrets.

Notes apps are generally not encrypted, a fact that surprised nearly 60 percent of respondents surveyed by DuckDuckGo on the subject. Almost half said that they used their notes app to save usernames, passwords, Social Security numbers, credit card information, and security or PIN codes. Keeping this info in a notes app makes it susceptible to anyone who has physical access to your phone and to hackers who gain access to a network you're on—or who siphon your data using a public charging station.

So though a notes app may be your go-to, consider using it only for data that's not sensitive (it's up to you if that includes your breakup poems). To keep your passwords secure, use a password manager such as Dashlane or Keeper. And for notes that should remain secure, choose an encrypted notes app such as Standard Notes.