The company was using a denial-of-service attack through hundreds of computers in Asia to cripple the sites where its documents are available, the report said.
One of the sources told Re/Code Sony was using Amazon Web Services (AWS), Amazon Inc's cloud computing services.
"The activity being reported is not currently happening on AWS," a spokesperson said in an email to Reuters.
"AWS employs a number of automated detection and mitigation techniques to prevent the misuse of our services," the spokesperson said.
"In cases where the misuse is not detected and stopped by the automated measures, we take manual action as soon as we become aware of any misuse."
Sony Pictures Entertainment was not immediately available for comment.
Hackers released sensitive data over the Internet, including employee salaries, social security numbers and high-quality digital versions of several unreleased films.
A group calling itself Guardians of Peace claimed responsibility for the cyber-attack that shut down most of the studio's network for more than a week.
© Thomson Reuters 2014
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