Additional Details
When an infected workbook is opened, X97M/Smack.A disables the
built-in macro virus protection of Excel and removes the
"Tools/Macro..." menu.
Then the virus copies the active workbook to Excel's starup directory
as the name "XLDATA.XLS". After this has been done, the virus infects
all workbooks that are opened.
It activates its payload at September 10th. At this time it shows a
message box with the following text:
You know what?
You're getting OLD, man!!!
[Analysis: Sami Rautiainen, F-Secure]