According to media reports, the compromised data had been stored on three spreadsheet files which contained personal information on more than 5,000 customers, including Social Security numbers.
The files were traced to a home computer in Florida reportedly owned by a former ABN Amro employee.
P2P systems have become increasingly dangerous for enterprises. The file-sharing services are part of a group of applications commonly referred to as 'greynets'.
Data from greynet traffic can often bypass systems that monitor internet traffic because they do not use normal web page or email protocols.
A Seattle man was arrested earlier this month for using P2P clients to steal data from the machines of other users.
In July, a Japanese police officer lost his job after inadvertently allowing more than 6,600 police files to be leaked onto a P2P network.
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