Morgan Stanley discovered the post, containing client data, during a routine Internet check on Dec. 27 Reuters

Morgan Stanley announced Monday that it had fired a financial adviser who was accused of stealing information about 350,000 clients of the firm’s wealth management division.

According to the New York City-based financial services firm, there is no evidence of any economic loss suffered by its clients as a result of the latest breach, but it has been determined that some account information, including account names and numbers, of about 900 clients were briefly posted on the Internet for sale.

“Overall, partial account information of up to 10 percent of all Wealth Management clients was stolen. The data stolen does not include account passwords or social security numbers,” Morgan Stanley said in a statement, adding that the firm had notified “all potentially affected clients and instituting enhanced security procedures including fraud monitoring on these accounts.”

While Morgan Stanley did not mention the name of the terminated employee, a person familiar with the matter identified the person as Galen Marsh, a 30-year-old financial adviser, who worked at one of Morgan Stanley’s New York branches, Reuters reported. While it is still unclear how Marsh allegedly compromised the company's security measures to steal client information, the person close to the matter said that Marsh used an external application to post the stolen information online.

According to Robert Gottlieb, Marsh’s attorney, his client had admitted to obtaining the account information but denied claims that he posted some of the data online or tried to sell them.

“This is an employment matter between Mr. Marsh and Morgan Stanley,” Gottlieb was quoted by Reuters as saying. “He has acknowledged that he should not have obtained the account information and he has been cooperating fully with Morgan Stanley to protect the firm and its customers.”

Morgan Stanley discovered the online post, containing client data, during a routine Internet check on Dec. 27 and quickly took the information down. Marsh, who joined Morgan Stanley in April 2008 as a sales assistant and became a financial adviser in March last year, did not immediately respond to phone calls and messages seeking an explanation, Reuters reported.

“We are today still focused on Social Security numbers, but an email address and a phone number can provide a gateway to getting more information about you and it is valuable information to identify individuals with big bank accounts,” Darren Hayes, assistant professor and director of cybersecurity at Pace University in New York, told the Wall Street Journal.

Morgan Stanley’s wealth management business has been a key driver of the firm’s success over the past few years. Revenues from the division rose 8.7 percent to reach $3.79 billion in the third quarter of 2014, the Journal reported.