Kukudro is an MS Word macro trojan dropper written in Visual Basic for Applications (VBA). The dropper has been spammed in various e-mails as my_Notebook.doc inside a zip archive. Once a user opens the document, it drops and runs a binary executable.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
When the infected Word document is opened, the macro code inside of it will be executed. It will decode a binary file from its code and drop it as 666inse_1.exe to the root of the C: drive. Then the macro will execute the dropped 666inse_1.exe file and end. The binary executable is a trojan downloader called Small.dcu.
Please note that you are using Office 2003 or later the macro will be executed only if macros have been enabled from Word's security settings. Otherwise, the trojan uses a vulnerability in MS Word 97, 2000 and XP and will run although macros are disabled. You can find more about this vulnerability here: http://www.microsoft.com/technet/security/Bulletin/MS01-034.mspx.