The recent theft at UK's Tesco Bank was most likely caused by an organized group of criminals cashing out cloned cards, according to analysts at security firm Digital Shadows.
Earlier this month, Tesco Bank confirmed an attack through which an estimated $3.1 million USD was stolen from about 9,000 accounts. At the time the Tesco thefts were initially reported, there was little information on how the attack was performed. To narrow down the sources, Digital Shadows has applied a technique called the Analysis of Competing Hypothesis (ACH) to the available data.
The ACH is "a structured analytical technique" analysts can use to determine the consistency and inconsistency of all data points with a collection of potential hypotheses. While experts could not definitively eliminate any of the hypotheses examined, they found some causes were more likely than others.
Read more about Digital Shadows' methodology and results on the company's blog.