Hackers have obtained personal information of more than 38 million Adobe customer accounts during a cyber-security breach revealed about a month ago, which is far bigger compared to the initially reported 2.9 million users.

According to the software maker, hackers had pinched part of the source code to Photoshop editing software, which is extensively used by photography professionals.

The cyber security breach, reported on 03 October, saw hackers accessing Adobe users’ names in addition to credit and debit card numbers and expiration dates.

Adobe spokesperson Heather Edell was cited by Krebs as saying that the firm has completed a campaign to contact active users whose user IDs with valid, encrypted password information was stolen, advising those users to reset their passwords.

"So far, our investigation has confirmed that the attackers obtained access to Adobe IDs and, encrypted passwords for approximately 38 million active users," Edell said.

"We have completed email notification of these users.

"We also have reset the passwords for all Adobe IDs with valid, encrypted passwords that we believe were involved in the incident — regardless of whether those users are active or not."

Reports reveal that hackers were able to use those passwords to break into other accounts as several users used the same passwords for multiple accounts.