Target’s 40 million credit and debit card numbers and names and contact information of up to 70 million people were stolen in the Target data breach in 2013. The retailer is facing lawsuits by small banks looking to recover their losses. Experts have posited a few compelling theories as to how the breach happened. One theory is that network segmentation and tightly controlled access to sensitive data are critical. Another theory: The breach may have resulted partly from the retailer’s failure to segregate systems handling sensitive card data from the rest of its network.”]
Source: https://www.darkreading.com/attacks-breaches/lessons-learned-from-the-target-breach