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Chronicles

The story behind the story

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AT&T confirms data dumped online appears to be from 2019 or earlier and has personal data of 7.6M current and 65.4M former account holders, resets passcodes

US telco giant takes action after 2019 data breach  —  Phone giant AT&T is reseting customer account passcodes after a huge cache …

TechCrunch Zack Whittaker

Context & Ripple Effects

The disclosure follows a dataset dump affecting roughly 73 million AT&T customers that put unresolved questions about the source of the records at the center of the coverage. AT&T has now tied the material to data from 2019 or earlier and responded with a credential-control measure.

The scale spans both current and former account holders, making this more than a service-continuity issue: historical customer records can remain consequential after an account relationship ends.

First-order effects

  • AT&T is resetting passcodes for current customers, disrupting existing account access while reducing the usefulness of any exposed account credentials.
  • The 7.6 million current and 65.4 million former account holders whose personal data appears in the dump face renewed exposure to phishing and other impersonation attempts based on that information.

Second-order effects

  • AT&T’s support, authentication, and fraud teams will have to absorb reset-related customer contacts and watch for account-recovery abuse, not just unauthorized logins.
  • Other telecom providers may face pressure to reassess how long they retain customer data and how quickly they can force credential resets when older datasets resurface.

Third-order effects

  • If large, older customer datasets continue to reappear online, breach response will increasingly be judged by lifecycle controls—retention, deactivation, and account recovery—not solely by whether a system is currently secure.
  • The later notification of another breach involving phone records for nearly all AT&T customers underscores how repeated incident disclosures can compound trust and oversight pressure even when the datasets differ.

The trend: Telecom security is shifting toward managing the long-lived risk of customer data and credentials after they leave active systems, not merely containing a single incident.

Discussion

  • @kennwhite@mastodon.social Kenn White on mastodon
    Great story by @zackwhittaker and nice research by @chick3nman.  PSA: don't use deterministic hashing/encryption schemes to hide sensitive data on low-cardinality fields.  —  Shorter version: don't try to protect critical national infrastructure without consulting a cryptography …
  • @zackwhittaker@mastodon.social Zack Whittaker on mastodon
    More: Security researcher Sam “Chick3nman” Croley told TechCrunch how he figured out that the encrypted records in the 73 million AT&T leaked data set were customer account passcodes.  —  Croley said it was not necessary to crack the encryption cipher to unscramble the passcode d…
  • @HoustonDog@mastodon.world @HoustonDog@mastodon.world on mastodon
    @Techmeme  —  #ATT first denied it for 10+ days  —  * it was obvious to me — my 2002 master account; never used elsewhere (I had subaccounts)
  • @noahsbwilliams Noah Williams on x
    I don't usually shit on people for InfoSec fails, but the execs at telcos are some of the dumbest, most negligent motherfuckers in all of history. They only see dividends and stock prices and I guarantee you they were warned about this and told the security people to fuck off.
  • @vsikka Vishal Sikka on x
    Totally agree @demishassabis
  • @lorenzofb Lorenzo Franceschi-Bicchierai on x
    The data dumped earlier this month is from 2021, and was initially dismissed by AT&T as not a data breach. But a security researcher who analyzed the leaked data told us the encrypted account passcodes are easy to decipher. Now AT&T has taken action. https://techcrunch.com/...
  • @mattrosoff Matt Rosoff on x
    More from @zackwhittaker; Security researcher Sam “Chick3nman” Croley told TechCrunch how he figured out that the encrypted records in the 73 million AT&T leaked data set were customer account passcodes. Encryption did not have to be cracked. Deets: https://techcrunch.com/...
  • @morningbrew @morningbrew on x
    AT&T reported today that the data of 73 million current and former customers has leaked on the dark web • AT&T reset passcodes of current customers • info leaked included names and SSNs • data was from 2019 or earlier AT&T said there was no evidence of a system breach
  • @lorenzofb Lorenzo Franceschi-Bicchierai on x
    NEW SCOOP: AT&T has reset millions of customer account passcodes after a huge cache of data containing customer records was dumped online this month. AT&T said breach impacted ~7.6 million current customers and ~65.4 million former customers. https://techcrunch.com/...
  • @mattrosoff Matt Rosoff on x
    Major scoop here from @zackwhittaker resets account passcodes after millions of customer records leak online. This is the first time that AT&T has acknowledged that the leaked data belongs to its customers. https://techcrunch.com/... via @techcrunch tip @techmeme
  • r/privacy r on reddit
    AT&T resets account passcodes after millions of customer records leak online US telco giant takes action after 2019 data spill
  • r/technology r on reddit
    AT&T confirms data breach and resets millions of customer passcodes
  • r/ATT r on reddit
    AT&T Addresses Recent Data Set Released on the Dark Web