Microsoft has played down a feature in open source rival OpenOffice.org that removes some password protection on Office applications.

When users open someone else's Excel file in OpenOffice.org's Calc (the OpenOffice equivalent of Excel) it removes any password protection applied to cells and worksheets by the author, so that hidden information can be read, edited and saved.

It is still possible to protect an entire Excel document with passwords. But removing cell and sheet protection could lead to accidental changes being saved by others sharing an Excel document in OpenOffice.org.

The same is true for any password protection applied to elements of a Word document opened using OpenOffice.org's Writer application.

Darren Strange, Office product manager at Microsoft, said that although the open source community had "not respected" the feature and that it could could present "a bit of a problem" to Office users, it was not "security feature".

"It works well for us but it is not a feature other vendors with different functionality would neccesarily have to implement. OpenOffice is not circumventing any security in Office here," said Strange.

He pointed out that the next version of Office, 2007 will include a beefed-up set of Information Rights Management tools, which will offer a higher level of security. Microsoft claims it will prevent screengrabs from being taken of sensitive documents.

John McCreesh, marketing project co-lead for OpenOffice.org, said that the removal of protection passwords from Excel files was a feature of Calc, not a bug.

He argued that OpenOffice users are warned that saving in the Excel format will remove the password. But he could not say how Excel users who create a file that will be used by others can protect hidden information from OpenOffice users.

Anyone that wants to protect passwords that will be opened in different spreadsheet applications should instead use the Oasis OpenDocument file format, which includes password protection, argued McCreesh.

"The user has already been warned that saving in Excel format will not be password protected; they then have to choose OpenDocument Format, where the 'Save with password' option is clearly visible," he said.

The Excel file format, he added, is a "dying legacy".

More information on protecting Excel files can be found on the Microsoft KnowledgeBase.