AT&T short codes exposes users to phishing scams

Computer programmer Dani Grant revealed that texts messages from AT&T are easy to spoof and expose customers to phishing scams.

AT&T customers are exposed phishing attacks due to proprietary AT&T’s text protocols. Computer programmer Dani Grant discovered that is quite easy to spoof text messages from AT&T. In this variant of “Phishing” attacks, crooks attempt to trick victims into revealing their sensitive data by sending text messages, containing short codes, that appear to be from legitimate companies.

Grant explained that AT&T uses different short codes that could be abused by attackers to trick company’s customers into phishing scams. AT&T customers are unable to distinguish between the legitimate short codes and phishing messages.

“It’s sent from a short code I’ve never seen, and prompts me to visit a URL that’s not obviously an AT&T site. It looks like phishing, but I’ll bet a lot of AT&T’s customers click on it anyway.” states Grant in a blog post.

AT&T handles its customer alerts via text messages, for this reason, cyber criminals try to reproduce this functionality for phishing attacks. Grant explained that attackers also use short codes as a social engineering tactic, the programmer highlighted that short codes are typically expensive, so users tend to believe that messages containing them are sent by a trustable entity. Threat actors could send AT&T alerts that appear like the legitimate one and AT&T customers have no way to discriminate them.

“Twilio charges a couple thousand dollars for them—so they could be seen as an indicator that a message is coming from a business, but a well-funded hacker would have no problem acquiring one, and I was able to find a free trial for 30 days of short code.” continues Grant.

As proof-of-concept, Grant used a free trial for 30 day service for short code and bought a domain that appears as legitimate ( for $10.89, then sent a message.

Grant demonstrated that was impossible to distinguish bogus messages from legitimate ones.


Another security issue is that some of AT&T legitimate links redirect users to domains not obviously associated with AT&T like and

Another problem is that AT&T directs customers to URLs like which aren’t obviously associated with AT&T,” Grant wrote. “Every AT&T text looks like this, so customers learn to trust any text that claims to be from AT&T, no matter on what they’re being asked to click.

Another element that generates confusion is the lack of a specific format for the AT&T text messages, as explained by Grant some messages start with all capital letters,  “AT&T FREE MSG”, in other cases in all lowercase: “AT&T Free MSG.”

Grant provided the following possible solutions to the security issue:

  • Use URLs that are subdomains or extensions of
  • Preload short codes as phone contacts for AT&T sold devices. That way, customers will know what numbers actually belong to AT&T and which do not.
  • A third option is for AT&T to communicate through other methods besides text messages. While there is certainly the tradeoff of convenience, emails from addresses or push notifications through AT&T’s app are alternatives.

Grant ethically reported the issues to AT&T, but the company hasn’t commented them.

Pierluigi Paganini

January 27, 2015

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