A high-level developer for a major Wall Street firm has been arrested by the FBI and charged with stealing computer code that automates high-volume trading on stock and commodities markets.

The Reuters news service, which broke the story yesterday, tied the developer, Sergey Aleynikov, to Goldman Sachs, where he was allegedly a vice president of equity strategy.

In the days before his 5th June resignation from Goldman Sachs, Aleynikov copied, encrypted and transferred approximately 32MB of proprietary code to a server located in Germany, the FBI claimed in the complaint filed on the 4th July by Special Agent Michael McSwain, a member of the agency's securities fraud squad.

Aleynikov resigned to take a job with a new company "that intended to engage in high-volume automated trading," for triple his $400,000 (£240,000) salary, the complaint said.

McSwain spelled out four data transfers from Aleynikov's workstation - both locally and remotely - on 1st, 4th and 5th June, then tied the dates and times to Aleynikov's use of his keycard to access the office, or logging in remotely from his home computer.

Aleynikov tried to cover his tracks, alleged McSwain. "The program used to encrypt the files was then erased," the FBI agent swore in the complaint. "An attempt was also made to erase the bash history, which was unsuccessful, because of a feature of the Financial Institution's computer system that retains a back-up copy of each user's bash history."

A "bash history" is a log of the most-recently-executed commands by a user on a Unix-based operating system.

The FBI arrested Aleynikov late on Friday night at the Newark Airport, and charged him with theft of trade secrets and transporting stolen property.

The complaint said that Aleynikov had made a statement after his arrest, admitting that he had copied and encrypted files from his company's servers, then transferred them to the remote server, deleted the encryption software and attempted to erase the bash history.

"Aleynikov claimed, however, that he only intended to collect 'open source' files on which he had worked, but later realised that he had obtained more files than he had intended," McSwain said.

As of 2:30 p.m. ET on Monday, Aleynikov was still being held in federal custody, pending bail. A Saturday hearing had set bail at $750,000 (£460,000), and placed both travel restrictions and computer access limitations on him assuming he posts a bond.

A spokeswoman for the US Attorney in the Southern District of New York declined to comment further on the case.