The social network initially turned off the feature last September after the account of CEO Jack Dorsey was hacked via messaging service CloudHopper, which enabled its users to tweet via text message after linking their mobile phone numbers to their accounts. Twitter acquired CloudHopper in April 2010.

Twitter turned the feature back on the following day for locations that depended on SMS to tweet.

Twitter Support tweeted Monday, “We want to continue to help keep your account safe. We’ve seen vulnerabilities with SMS, so we’ve turned off our Twitter via SMS service, except for a few countries. Everyone will still have access to important SMS messages needed to log in to and manage their accounts.”

The social network also confirmed to Matt Binder of Mashable that millions of inactive accounts that were created via SMS were deleted from its platform.

A Twitter spokesperson told Binder, “We are removing accounts that were created via SMS as we no longer support this technology and because these accounts have a high risk of becoming compromised. As a result of this, some accounts may see a drop in followers. We want people to have confidence that their follower counts are meaningful, accurate and reflect active accounts on Twitter, and this is part of our ongoing work to ensure that.”