When threat actors are able to extract sensitive information due to neglectful API implementations, the consequence is equivalent to a data breach and should be handled accordingly by the firm [and] examined by regulators,” Gal told TechCrunch.

Alon Gal, the co-founder and CTO of cybersecurity firm Hudson Rock, alerted Motherboard to the listing.

"A database of that size containing the private information such as phone numbers of a lot of Facebook's users would certainly lead to bad actors taking advantage of the data to perform social-engineering attacks [or] hacking attempts," Gal told Insider.

“In the case of the T-Mobile attack, the alleged hacker said they had different motivations. In a screenshot of a text conversation posted online by Alon Gal, co-founder of cybercrime firm Hudson Rock, the hacker appears to tell Gal that the attack was done “to harm US infrastructure.”