Twitter exploit let ‘bad actors’ match phone numbers to accounts

For dissidents around the globe, Twitter remains the tool of choice for speaking out against their repressive governments. 

With that in mind, it’s easy to see why today’s announcement from the social media company is so troubling. Twitter, in a Monday blog post and corresponding statement, announced it had discovered that “bad actors” with possible state-sponsored connections had found a way to tie phone numbers to Twitter accounts en masse. 

In other words, a hacker using this exploit could potentially reveal the identity of a person tweeting under a pseudonym who has their account tied to a phone number. Or, alternatively, it’s worth remembering that determining the phone number connected to an account is often a crucial step in hacking it. 

“On December 24, 2019 we became aware that someone was using a large network of fake accounts to exploit our API and match usernames to phone numbers,” reads the Twitter blog post. “While we identified accounts located in a wide range of countries engaging in these behaviors, we observed a particularly high volume of requests coming from individual IP addresses located within Iran, Israel, and Malaysia.” 

With Saudi Arabia’s documented real-world harassment of dissidents, for example, it’s easy to see how such exploits could lead to real-world harm. 

“It is possible that some of these IP addresses may have ties to state-sponsored actors,” continued the blog post.

We’ve reached out to Twitter to determine how many users were affected and if the company planned to notify users whose phone numbers were tied to accounts in the manner described. We’ve received no immediate response at present. 

Importantly, not everyone was vulnerable to this specific exploit. According to Twitter, the bad actors in question could only tie your account to a phone number if your account met two specific criteria. 

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First, you had to have added a phone number to your account. However, with many people doing that very thing to enable two-factor authentication, a lot of folks fall into that bucket. Secondly, and this should narrow things down a bit, you must have selected the “Let people who have your phone number find you on Twitter” option. 

Now would be a good time to make sure you don’t have that setting enabled. It would also be a great time for Twitter to consider removing it altogether.