Users of OpenOffice may be more vulnerable to viruses than they would be with Microsoft's own product.

Researchers at the French Ministry of Defence have found that the open source software is highly vulnerable.

"The general security of OpenOffice is insufficient," wrote researchers in a paper entitled In-depth analysis of the viral threats with OpenOffice documents. "This suite is up to now still vulnerable to many potential malware attacks," they continued.

The paper describes four proof-of-concept viruses that illustrate how maliciously encoded macros and templates could be created to compromise systems running the open-source software.

"The viral hazard attached to is at least as high as that for the Microsoft Office suite, and even higher when considering some... aspects."

The report was written by researchers at the French Ministry of Defence's Signal Corps and is set to be published in the Journal in Computer Virology, a Paris-based academic journal for computer scientists.

A number of the problems described in the report have to do with the basic design of the software. For example, OpenOffice does not perform adequate security checks on the software it runs, the researcher said.

And because of the extreme flexibility of the free office suite, there are many ways for writers to create malicious macros, the researchers found.

The OpenOffice team has already fixed a software bug discovered by the French researchers, and the two groups are in discussions about how to improve the overall security of the software, said Louis Suarez-Potts, an community manager.

"The one real flaw in the programming logic has been fixed," Suarez-Potts said. "The others are theoretical."

OpenOffice has patched a number of vulnerabilities in the past few weeks, and Suarez-Potts says users should upgrade to the latest version.

These latest bugs show that the open-source project has some security work ahead of it, said Russ Cooper, a senior information security analyst at Cybertrust. "If these types of vulnerabilities had been discovered in Microsoft Office, it would be front-page news," he said.

"Whoever did the security for OpenOffice has totally ignored what Microsoft has gone through with the security of their own Office documents."

Attackers have exploited a number of bugs in Microsoft's Office applications of late, sending maliciously encoded Word, Excel and PowerPoint documents via e-mail to a small number of victims in extremely targeted attacks.

Last week, Microsoft patched the latest such flaws, which related to PowerPoint.

Signal Corps Researcher Eric Filiol has also discussed some of the team's findings during a conference presentation.

(Peter Sayer contributed to this report.)