Portland-based iovation, which provides software to help online businesses screen potential customers for probability of fraud and abuse, said its tracking data shows that Linux devices are the source of the highest percentage of fraudulent transactions. The company--which helps firms ferret out those fraudulent transactions--said its tracking found that Linux machines had the highest rate of fraud (2.3 percent), followed by Windows (1.4 percent), then OS X machines (1 percent). The company said it believes the reason for the ranking is that fraudsters prefer operating systems that make it easier to automate their schemes. The company said it is now tracking over a billion devices, tying those devices to risk of fraud committed online.