One reason, he suggested, is the Bitcoin users haven't hit critical mass, and the effort of writing malware targeting it is not currently worth it.
"Attackers are still making enough money from banking accounts," he said. "And if you infect someone's laptop, the chances of them using online banking is pretty high. But the percentage of people using digital currency is really a tiny fraction."
Meanwhile, as Apple, Google and Samsung begin to roll out mobile payments, he expects to see criminals to start paying attention soon.
"At the moment, we haven't seen the Trojans targeting those yet," he said. "But we do expect this year for attackers to look into it. If you can infect a mobile phone that can be used as a credit card, that is real money for attackers."
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