The attack that planted malware on Target’s point of sale (POS) terminals in November’s huge data breach used inside knowledge of the network rather than a vulnerability in its retail software, McAfee has said in its latest quarterly analysis.

Snippets of information on the attack’s engineering have been trickling out steadily since Target made the incident public in January, but this one suggests if not complexity then at least a degree of planning.

As has been widely discussed, the Target attack deployed the off-the-shelf BlackPOS, a generic but hugely popular toolkit used by criminals to capture data on retail computers connected to the card readers used by customers.  

The behaviour of malware inside Target’s network was controlled by scripts that referenced the network’s internal structure in some detail. “Details regarding Active Directory domain names, user accounts, and IP addresses of SMB shares were hardcoded into scripts that were dropped by some of the malware components,” said McAfee.

Although not a hugely surprising finding, it does suggest that attackers are able to beat security even when they are not familiar with the POS software in use by the firm they are targetting. This was no speculative smash and grab on a company that hadn’t secured its assets; the criminals knew what they were doing and had gathered enough data to launch the attack with precision.

The fact they were able to do this underscores the size of the security failure that occurred to allow hackers to make off with the personal details of between 70 and 110 million of the shop’s customers.

The data stolen had been removed in the clear, without encryption, using FTP, McAfee said. The thieves were now selling the stolen account details in batches of a few million at a time on carding forums.

The attackers are believed to have penetrated the retailer’s network by exploiting remote access credentials lifted from an air conditioning firm. According to the FBI, the BlackPOS malware toolkit is the handiwork of a teen Russian programmer from St Petersburg although it is likely that a separate gang carried out the attack. 

Other US retailers affected by POS attacks in 2013 include Neiman Marcus, White Lodging, Harbor Freight Tools, Easton-Bell Sports, and Michaels Stores. Only days ago, Target's CIO resigned in the wake of the breach.

“These cyber thefts occurred at a time when most people were focused on their holiday shopping and when the industry wanted people to feel secure and confident in their purchases. The impact of these attacks will be felt both at the kitchen table as well as the boardroom table,” said McAfee Labs senior vice president, Vincent Weafer.

“For security practitioners, the ‘off the shelf’ genesis of some of these crime campaigns , the scale of operations, and the ease of digitally monetizing stolen customer data all represent a coming of age for both Cybercrime-as-a-Service and the ‘dark web’ overall.”