AT&T data breach affected nearly all customers after info downloaded to 3rd-party platform

The data of nearly all customers of the U.S. telecommunications giant AT&T was downloaded to a third-party platform in a security breach, the company said Friday, as cyberattacks against businesses, schools and health systems continue to spread globally.

The breach, most of which took place over five months in 2022, hit customers of AT&T's cellular customers, customers of mobile virtual network operators using AT&T's wireless network, as well as its landline customers who interacted with those cellular numbers.

Approximately 109 million customer accounts were impacted, according to AT&T, which said that it currently doesn't believe that the data is publicly available.

"The data does not contain the content of calls or texts, personal information such as social security numbers, dates of birth, or other personally identifiable information," AT&T said Friday.

The compromised data also doesn't include some information typically seen in usage details, such as the time-stamps of calls or texts, the company said, or customer names. AT&T, however, said that there are often ways using publicly available online tools to find the name associated with a specific telephone number.

Cyber-security experts concurred, saying that such data can be used to trace users.

"While the information that was exposed doesn't directly have sensitive information, it can be used to piece together events and who may be calling who. This could impact people's private lives, as private calls and connections could be exposed," Thomas Richards, principal consultant at Synopsys's software integrity group, said in an emailed statement.

"The business phone numbers will be easy to identify and private numbers can be matched to names with public record searches."

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Third-party platform identified as Snowflake

An internal investigation determined that compromised data includes AT&T records of calls and texts between May 1, 2022 and Oct. 31, 2022.

AT&T identified the third-party platform as Snowflake and said that the incident was limited to an AT&T workspace on that cloud company's platform and did not impact its network.

Cyber-security experts say the sheer volume of data held be companies on cloud platforms can create its own perils.

"The AT&T data breach underscores the growing risks associated with the vast amounts of data companies now store on cloud and SaaS platforms," said Roei Sherman, field chief technology officer at Mitiga, a threat-detection and -investigation company that focuses on cloud technology.

"As organizations increasingly rely on these technologies, the complexity of detecting and investigating breaches has risen sharply."

AT&T's investigation is ongoing and it has engaged with cyber-security experts to understand the nature and scope of the criminal breach. At least one person has been apprehended so far, according to the company.

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The Federal Bureau of Investigation said that it has worked collaboratively with AT&T and the Justice Department "through the first and second delay process, all while sharing key threat intelligence to bolster FBI investigative equities and to assist AT&T's incident response work."

The Department of Justice said Friday that it became aware of the breach early this year, but that it met the security standard for a delayed filing by AT&T with the U.S. Securities & Exchange Commission, a filing that was made public Friday.

The DOJ said an earlier disclosure of the breach would "pose a substantial risk to national security and public safety."