Target confirmed Friday that the hack attack against the retailer's point-of-sale (POS) systems that began in late November triggered alarms, which its information security team evaluated and chose to ignore.

"Like any large company, each week at Target there are a vast number of technical events that take place and are logged. Through our investigation, we learned that after these criminals entered our network, a small amount of their activity was logged and surfaced to our team," said Target spokeswoman Molly Snyder via email. "That activity was evaluated and acted upon."

Unfortunately, however, the security team appears to have made the wrong call. "Based on their interpretation and evaluation of that activity, the team determined that it did not warrant immediate follow up," she said. "With the benefit of hindsight, we are investigating whether, if different judgments had been made, the outcome may have been different."

[Collaboration with competitors may be the key to slowing security threats. See Retail Industry May Pool Intel To Stop Breaches.]

Target arguably wasn't breached because it failed to invest in proper information security defenses. In fact, Snyder said the company had "invested hundreds of millions of dollars in data security, had a robust system in place, and had recently been certified as PCI-compliant." Likewise, the retailer apparently heeded multiple warnings from US-CERT -- part of the Department of Homeland Security -- about the increasing threat of POS-malware attacks against retailers.

Unusually for a retailer, Target was even running its own security operations center in Minneapolis, according to a report published Thursday by Bloomberg Businessweek. Among its security defenses, following a months-long testing period and May 2013 implementation, was software from attack-detection firm FireEye, which caught the initial November 30 infection of Target's payment system by malware. All told, up to five "malware.binary" alarms reportedly sounded, each graded at the top of FireEye's criticality scale, and which were seen by Target's information security teams first in Bangalore, and then Minneapolis.

Image credit: Jay Reed on Flickr.

When reviewing Target's log files, digital forensic investigators also found the November 30 alerts, as well as multiple alerts from December 2, all of which tied to attackers installing multiple versions of their malware -- with the alerts including details for the external servers to which data was being sent -- Bloomberg Businessweek reported. Later on December 2, attackers began siphoning 40 million credit and debit card numbers from POS terminals, as well as personal information on 70 million customers. Ultimately, they exfiltrated at least 11 GB of data, according to Aviv Raff, CTO of Israel-based cybersecurity technology company Seculert, which found one of three FTP servers to which the data was sent. From there, the data was transferred to a server hosted by Russian-based hosting service vpsville.ru.

Obviously, had Target's security team reacted differently, they might have contained what turned into a massive data breach. But the security team didn't even have to be in the loop. The FireEye software could have been set

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