Hackers used phishing emails to break into a Virginia bank in two separate cyber intrusions over an eight-month period, making off with more than $2.4 million total. Now the financial institution is suing its insurance provider for refusing to fully cover the losses.

According to a lawsuit filed last month in the Western District of Virginia, the first heist took place in late May 2016, after an employee at The National Bank of Blacksburg fell victim to a targeted phishing email.

The email allowed the intruders to install malware on the victim’s PC and to compromise a second computer at the bank that had access to the STAR Network, a system run by financial industry giant First Data that the bank uses to handle debit card transactions for customers. That second computer had the ability to manage National Bank customer accounts and their use of ATMs and bank cards.

Armed with this access, the bank says, hackers were able to disable and alter anti-theft and anti-fraud protections, such as 4-digit personal identification numbers (PINs), daily withdrawal limits, daily debit card usage limits, and fraud score protections.

National Bank said the first breach began Saturday, May 28, 2016 and continued through the following Monday. Normally, the bank would be open on a Monday, but that particular Monday was Memorial Day, a federal holiday in the United States. The hackers used hundreds of ATMs across North America to dispense funds from customer accounts. All told, the perpetrators stole more than $569,000 in that incident.

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But just eight months later — in January 2017 according to the lawsuit — hackers broke in to the bank’s systems once more, again gaining access to the financial institution’s systems via a phishing email.

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Prior to executing the second heist, the hackers used the bank’s Navigator system to fraudulently credit more than $2 million to various National Bank accounts. As with the first incident, the intruders executed their heist on a weekend. Between Jan. 7 and 9, 2017, the hackers modified or removed critical security controls and withdrew the fraudulent credits using hundreds of ATMs.

All the while, the intruders used the bank’s systems to actively monitor customer accounts from which the funds were being withdrawn. At the conclusion of the 2017 heist, the hackers used their access to delete evidence of fraudulent debits from customer accounts. The bank’s total reported loss from that breach was $1,833,984.

Source: Hackers Breached Virginia Bank Twice in Eight Months, Stole $2.4M — Krebs on Security