On Friday, Twitter said it would only allow paid subscribers to use text messages as a two-factor authentication (2FA) method to protect their accounts.

After March 20, “only Twitter Blue subscribers will be able to use SMS as their two-factor authentication method,” the company tweeted.

Two-factor authentication is designed to make accounts more secure by requiring account holders to use a second authentication method and password. Twitter allows 2FA via text messages, authenticator apps, and security keys.

The company believes phone number-based 2FA is being abused by “bad actors,” according to a Wednesday blog post linked to the company’s tweet.

Twitter owner Elon Musk responded to a user tweet saying the company was changing its policy “because telcos use bot accounts to send 2FA text messages” and that the company is “responsible for scams every year.” text message” lost $60 million.

Previously it was free for verified accounts of politicians, celebrities, journalists and other public figures. The blue check mark is now open to anyone ready to pay.

Last month, Twitter said it would price a Twitter Blue subscription for Android at $11 per month, the same as iOS subscribers.