WASHINGTON (AP) — Morgan Stanley has agreed to pay $4 million to settle federal charges of failing to prevent the unauthorized purchase of $525 million in Apple stock by one of its customers.

The Securities and Exchange Commission announced the settlement Wednesday with the big Wall Street bank. The SEC said Morgan Stanley violated a rule requiring brokerage firms to have strong risk measures in place before they give customers access to the markets.

In this case, a trader at customer firm Rochdale Securities made orders to buy Apple stock in October 2012 that exceeded Rochdale's trading limits, according to the agency. The trader used the stock purchases to commit fraud by personally profiting from the trades, the SEC said.

New York-based Morgan Stanley neither admitted nor denied wrongdoing but did agree to refrain from future violations of the rule involved in the case, known as the market access rule. The SEC also censured Morgan Stanley, bringing the possibility of a stricter sanction if the alleged violation is repeated.

"Morgan Stanley has updated its written procedures to address the issue identified in the SEC's order and is pleased to have this matter behind it," Morgan Stanley said in a statement.

The unauthorized stock purchases by the trader, David Miller, caused Rochdale to suffer a $5.3 million loss and were blamed for bringing the demise of the firm. Rochdale, which was based in Stamford, Connecticut, stopped doing business last year and filed for bankruptcy protection this fall.

Miller pleaded guilty to criminal charges of conspiracy and fraud, and was sentenced to two and a half years in prison in November 2013.