Heat System Called Door to Target for Hackers - NYTimes.com

A very expensive network security lesson

"Investigators say they believe they have identified the entry point through which hackers got into Target’s systems, zeroing in on the remote access granted through the retailer’s computerized heating and cooling software, according to two people briefed on the inquiry.
The latest revelation highlights the reality that a large company is actually a sprawling network of interconnected vendors, and that weak security at any one vendor can lead to a breach that costs hundreds of millions of dollars. "

Heat System Called Door to Target for Hackers - NYTimes.com