Which 2013 attack on Target exposed payment-card data from about 40 million customers?

The Target data breach was the 2013 attack that exposed payment-card data from about 40 million customers.

Attackers entered Target’s network using credentials stolen from an HVAC contractor and then moved into systems connected with the retailer’s payment environment. Malware installed on point-of-sale systems captured payment-card information during transactions.

Target announced that information from approximately 40 million credit and debit cards had been stolen. A later disclosure said additional personal information connected with up to 60 million customers had also been affected, making the incident larger than the initial payment-card figure alone.

The breach is a classic example of third-party risk and network segmentation problems. It is separate from the Home Depot breach, which affected another major retailer in 2014.