The SEC alleges that hackers used the account, which is in the name of JSC Parex Bank, based in Riga, Latvia, to launch a pump and dump scheme involving the stocks of fifteen different Nasdaq-listed companies.

From at least December 2005 through December 2006 fraudsters hacked into and looted online brokerage accounts at seven different firms and used the funds to artificially inflate the price of the stocks, which were then sold off at a profit.

Accounts held at E-Trade Securities, Scottrade, TD Ameritrade, Vanguard, Fidelity Investments, Merrill Lynch and Charles Schwab were targeted by the scam, which netted the hackers $732,941 in illegal profits and cost the brokerages around $2 million in losses.

The Latvian bank's account was held at Pinnacle Capital Markets of North Carolina, says the SEC, while the accounts owners are thought to be located in Russia, Lithuania, Latvia and the British Virgin Islands.

John Reed Stark, chief of the SEC's Office of Internet Enforcement, says: "These perpetrators effectively cut out the middleman of the old fashioned pump-and-dump scheme, eliminating phony stock promotions, creating their own artificial trading demand, and consummating their frauds in as little time as a couple of hours."

The SEC says the fraudsters could not be identified because they used "electronic means" to cover their tracks and identities. Stark has admitted to reporters that the regulator still doesn't know the identity of the hackers.

The SEC says the enforcement action is the third filed in as many months involving market manipulation schemes conducted by hacking online accounts. In December the regulator froze the assets of Grand Logistic, a Belize corporation located in Tallinn, Estonia, and its owner, Evgeny Gashichev.