The person Goldman Sachs recently had arrested, was a person who was a specialist in intercepting and indexing network routing information and may just possibly have used security access codes and built a system to acquire trading information PRIOR to transaction_commit time points at NYSE.
The profitability of this split-second information advantage would have been and could have been extraordinary. Observed yielding profits at $100,000,000 a day.
GS has special access inside the system from its status assisting the Working Group on Financial Markets (colloquially the Plunge Protection Team) created by Presidential Order two decades ago. GC also acts as Special Liquidity Provider for NYSE.
Here is the most complex system that Mr. Aleynikov, the arrested employee worked on.
Strategic Telecom Optimized Routing Machine
Inventors: Sergey Aleynikov
Agents: OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
Assignees: IDT Corporation
Origin: ALEXANDRIA, VA US
IPC8 Class: AH04M700FI
USPC Class: 37922101
The patent application is a public document.
Basically GS might be using a program to intercept network traffic to determine, milliseconds in advance, when other participants will be active in the electronic market by detecting changing levels and types of network traffic.