Most of these specialized trading applications are well designed and have good security, but they are installed in untrusted environments, so it's hard to protect them, Komarov said. The customer's PC security is the main issue, he said.
There have been previous reports of hackers compromising online brokerage accounts. Those attacks primarily used form grabbers and Web injects like those seen in online banking malware, Komarov said.
Targeting online trading accounts is part of a big and growing trend for cybercriminals, he said.