U.S. securities firms are being told to keep their “instant messages” on file for at least three years.

NASD, the SRO of U.S. brokerages, said Wednesday that its member firms should also ensure that instant message communications do not violate NASD rules governing sales literature and correspondence.

“NASD recognizes that instant messaging is becoming increasingly popular as a real-time method of communicating and we want to be clear about our expectations for its use,” said Mary Schapiro, NASD vice chairman and president of Regulatory Policy and Oversight. “Firms have to remember that regardless of the informality of instant messaging, it is still subject to the same requirements as e-mail communications and members must ensure that their use of instant messaging is consistent with their basic supervisory and record keeping obligations.”

The NASD said that instant messaging is a developing technology that can pose supervisory and record keeping challenges for brokerage firms. Many firms have determined that they cannot adequately supervise instant messaging communications and have banned the use of instant messaging for communication with the public. Members are advised to evaluate instant messaging according to the “content and audience” of the instant messaging communications.

NASD members must supervise the use of instant messaging the same way they currently do for written and electronic communications. If a member firm is unable to establish an adequate supervisory program, the member must prohibit the use of instant messaging by its employees in customer communications, the NASD said.