The data compromise included names and ID numbers, but no financial information or bank account numbers. Shoprite has notified the Information Regulator.
Shoprite said that affected customers will receive an SMS to the cell number supplied at the time of the transaction.
"An investigation was immediately launched with forensic experts and other data security professionals to establish the origin, nature, and scope of this incident. Additional security measures to protect against further data loss were implemented by amending authentication processes and fraud prevention and detection strategies to protect customer data. Access to affected areas of the network has also been locked down," the company said.
It added, "Investigations are ongoing. The group is not aware of any misuse or publication of customer data that may have been acquired, however, web monitoring relating to the incident continues."
There is a possibility that the impacted customer data may be used by the unauthorised party and Shoprite advised customers to follow these precautionary measures:
• Do not disclose personal information such as passwords and PINs when asked to do so by anyone via telephone, SMS or email.
• Change passwords regularly and never share them with anyone else.
• Verify all requests for personal information and only provide it when there is a legitimate reason to do so.
• Should any unauthorised activity be detected, customers should immediately notify the group or relevant authorities.
Shoprite "apologises to those affected".
Customers with any questions or concerns may contact 0800 01 07 09 or email email@example.com.