Motherboard verified the tool, which comes in the form of a bot on the social network and messaging platform Telegram, outputs accurate phone numbers of Facebook users that aren’t included in the dataset of 500 million users.

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Motherboard then took phone numbers from the Telegram bot and entered them into Have I Been Pwned, a breach notification service run by security researcher Troy Hunt, who has uploaded the database of 500 million Facebook users into the service. None of the numbers Motherboard tested appeared in that dataset, according to Have I Been Pwned tests.

Motherboard also shared the data obtained from the bot with Alon Gal, co-founder and CTO of cybersecurity intelligence firm Hudson Rock who first tweeted about the recent 500m dataset. He said that none of the numbers obtained from the bot appear in the 500m dataset.

A literal sieve