MALL.cz Data Breach (2017): What Was Exposed & What To Do

What happened

The incident came to public attention on 27 July 2017, when the exposed records appeared on a publicly accessible site. The affected accounts belonged to users who had registered before 2015. Passwords in the posted data were present in plain text, although the company had stored them as hashes using several algorithms of differing strength over time. Only accounts whose passwords had apparently been cracked were included in the published set.

How a breach like this happens

Incidents involving the later publication of customer records from online retailers often begin with unauthorised access to internal systems, followed by extraction of user databases. Once obtained, the data may be processed offline to recover passwords from stored hashes. When the resulting files are placed on public sites, the original compromise may already be months or years old, and the exact entry point frequently remains undisclosed.

Who is MALL.cz?

MALL.cz operates as a major online marketplace in the Czech Republic, selling a wide range of consumer goods directly to individuals. Like similar retailers, it maintains accounts that store contact details and credentials to support orders, deliveries and customer service. A breach at such a service therefore touches a large number of ordinary shoppers who provided personal information in the ordinary course of making purchases.

The information in question

The published records contained email addresses, names, phone numbers and passwords. The company stated that only accounts created before 2015 were affected. No further categories of data, such as payment card details or order histories, were named in the available reporting.

What's at stake

Individuals whose email addresses and passwords appear in such incidents face the possibility that the same credentials are tried on other services. Phone numbers can be used for targeted contact or verification bypass attempts. For the organisation, the event requires notification to regulators and customers, along with a review of password-storage practices that had evolved over several years.

Were you affected?

Anyone who created a MALL.cz account before 2015 can check whether their email address appears in known breach records by using a free exposure scan service. Practical next steps include changing the password on that account and on any other site where the same password was used, and enabling two-factor authentication where available.

AICompiled with AI assistance from public sources and published under our editorial standards.