Custom Trojans are as hard for signature based anti-virus to catch as the dreaded zero-day threats which exploit previously unknown vulnerabilities.

FORBES: Modern malware requires modern methodologies to block

In effect, many of the big banks have turned themselves from businesses whose profits rose and fell with the capital-raising needs of their clients into immense trading houses whose fortunes depend on their ability to exploit day-to-day movements in the markets.

NEWYORKER: What Good Is Wall Street?

It gave rise to a cadre of day-traders who sought to exploit the new system.

FORBES: Guerrillas on Wall Street