Fazio Mechanical Services, a Maryland refrigeration contractor, is believed to be the entry point for the data breach at Target, which saw the loss of 40 million customer credit card details.

Prior reports had indicated that a service or supply company was the likely source of the attack and has now focused on Fazio. Brian Krebs, the security researcher, cited sources within the investigation that indicated Fazio of being the source of the credentials used by the attackers.

It is now believed that the attackers targeted Fazio to gain the credentials which then allowed access to Target's networks. Fazio said that it had access to Target's network in order to manage "electronic billing, contract submission and project management."

"Like Target, we are a victim of a sophisticated cyber attack operation," said president and owner Ross Fazio.

"We are fully cooperating with the Secret Service and Target to identify the possible cause of the breach and to help create proactive remedies to enhance the security of client/vendor connections to make them less vulnerable to future breaches."

The company installs and services refrigeration systems for supermarket locations.