The CERT Coordination Center is warning Internet users to beware of a new e-mail-borne threat that could allow an attacker to run malicious code on a victim’s computer.

The new threat, known as “Peido-B,” “VBS/Inor.B” or “Mother’s Day Virus” arrives in an e-mail that masquerades as an administrative message.

The e-mail contains the text “THIS IS A WARNING MESSAGE ONLY YOU DO NOT NEED TO RESEND YOUR MESSAGE” and contains an executable attachment named “sys_con.hta,” according to an alert posted by Sophos PLC.

When recipients launch the attachment, a trojan program known as “Troj/DLoader-BO” is installed on the user’s system. Trojan programs are malicious software, often masked as legitimate programs, that secretly compromise computer security.

Troj/Dloader-BO downloads and executes a file from the Web site within three days of being run for the first time and modifies the configuration of the Microsoft Corp. Windows operating system so that the program is started along with Windows, according to Sophos.

The warning from CERT appeared on the organization’s Web page under the heading “Current Activity,” which CERT said is reserved for “frequent, high-impact types of security incidents currently being reported to the (CERT Coordination Center).” CERT is based at the Software Engineering Institute at Carnegie Mellon University in Pittsburgh.

Despite that fact, Sophos, one of the few antivirus companies that did issue an alert for Peido-B, said that it had received only “a small handful” of reports of individuals who had been infected by it, said Carole Theriault, an antivirus consultant at Sophos in Abingdon, England.

While the timing of the Peido-B virus may loosely coincide with the celebration of Mother’s Day on Sunday, neither the e-mail message nor the attachment that installs the trojan program seem tailored to the holiday, calling into question CERT’s characterization of the new threat as a “Mother’s Day Virus.”

CERT was not immediately able to comment on the alert. CERT encouraged users to install antivirus software and to update their virus information files, if necessary.

Companies should also consider other measures such as filtering files with an .hta extension and monitoring outgoing HTTP (Hypertext Transfer Protocol) for attempts to retrieve executable files, CERT said.