Twitter knows a lot about its users and their friends, including their phone numbers.

Twitter recently acknowledged the company downloads the entire address book of its mobile users, including email addresses and phone numbers, when they use the “Find Friends” app. Twitter keeps the data for 18 month, the Los Angeles Times reports.

The app lets Twitter users look for friends who also are registered users. The app says Twitter will “Scan your Contacts for people you already know on Twitter.” But it doesn’t note that all entries in the address book are stored.

A spokeswoman for Twitter tells the Los Angeles Times the company plans to update language used in the mobile app. Twitter users also can have their contact databases removed by using the “remove” link on Twitter’s webpage.

The website Venturebeat reports Twitter isn’t the only mobile social network that uploads users’ address books. Apps from Facebook, Foursquare and Yelp also upload e-mail addresses and phone numbers.

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