Summary
Trojan-Dropper:W97M/Kukudro is a trojan-dropper embedded in the macro code of a Microsoft Word document.
Removal
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First, check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
Technical Details
This malware was first spammed to various emails addresses, as zip archive file named my_Notebook.doc. Once a user opens the document, it drops and runs a binary executable. Later distributions runs may use varying names for the infected document.
The trojan-dropper is written in Visual Basic for Applications (VBA).
Execution
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. The macro will then execute the dropped 666inse_1.exe file and end.
The binary executable is a trojan-downloader called Small.DCU.
Note
In Office 2003 or later, the macro will only execute if macros have been enabled from Word's security settings.Otherwise, the trojan uses a vulnerability in MS Word 97, 2000 and XP; in this case, the macro will be able to execute even though macros are supposed to be disabled.
More information on this vulnerability is available at: https://www.microsoft.com/technet/security/Bulletin/MS01-034.mspx.
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