This attack could pose a serious security threat. You should take immediate action to stop any damage or prevent further damage from happening.
This Signature detects attempts to cause buffer overflow in Lotus Notes by sending a specially crafted file.
A stack-based buffer-overflow vulnerability affects the Lotus SpreadSheet 123 reader in Lotus Notes 8.5. Specifically, the 'wkssr.dll' library fails to properly validate sizes for 'type 09h' and 'type 1Bh' records. 'type 00h' and 'type 23h' records are also affected. (CVE-2010-0133)
The vendor has released updates to address these issues. Please see the references for more information.