Qatar National Bank acknowledged in an emailed statement today that it was looking into "an alleged data breach" after a file containing the purported account information began circulating online.
The bank did not say whether information in the files was legitimate or if its network had been breached, citing a policy of not commenting on reports shared on social media.
Four people identified in the files and reached by The Associated Press confirmed their personal information was authentic.
"Everything that they had was correct," said Gordon Hickey, who used to work for Al-Jazeera and now works as a freelancer in Ireland. "It's a complete personal breach. It's awful."
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The bank said it was coordinating with "all concerned parties" to investigate the matter and offered its assurance that there would be no financial impact for its clients or the bank.
"QNB Group places the highest priority on data security and deploying the strongest measures possible to ensure the integrity of our customers' information," it said.
It also included a folder named "Al-Thani," the name of Qatar's ruling family, which purported to include details on many of its members.
Al-Jazeera said its online security division has sent a message to all staff assuring them that its own internal networks have not been compromised.
"Our staff have been recommended to be vigilant, be prudent and change passwords for those who bank with QNB and report any suspicious activity," Al-Jazeera said in a statement.