Guess what? Yep, there's yet another type of malicious document going around. Like last time, it's a MIME file with an MSO file containing an OLE file.

The sample (schro_193B11.xls 7F8C5E8B7157B04FA8E9CEEF13C28AB9) is an Excel spreadsheet saved as a MIME file:

But this time, the compressed data is at another position inside the MSO file:

So I updated my oledump tool (V0.0.16) to search for compressed data inside MSO files (in stead of looking at a fixed position 50).

The string encoding used in the VBA code is interesting. It is reminiscent of RC4:

I also updated my plugin plugin_dridex with this encoding:

Didier Stevens
Microsoft MVP Consumer Security
blog.DidierStevens.com DidierStevensLabs.com