-MS Office commonly exploited since 2006
-Existing exploits in the wild exploit unexceptional the older OLESS file format.
-Currently no known bugs in the newer XML based MS Office format.
Some MS Office exploits since 2006
-CVE-2006-0009 Powerpoint MS06-012 (March 2006)
-CVE-2006-0022 Powerpoint MS06-028 (June 2006)
-CVE-2006-2492 Word MS06-027 (June 2006)
-CVE-2006-3434 Powerpoint MS06-062 (October 2006)
-CVE-2006-3590 Powerpoint MS06-048 (August 2006)
-CVE-2006-4534 Word MS06-060 (October 2006)
-CVE-2006-4694 Powerpoint MS06-058 (October 2006)
-CVE-2006-5994 Word MS07-014 (February 2007)
-CVE-2006-6456 Word MS07-014 (February 2007)
-CVE-2007-0515 Word MS07-014 (February 2007)
-CVE-2007-0671 Excel MS07-015 (February 2007)
-CVE-2007-0870 Word MS07-024 (May 2007)
-CVE-2008-0081 Excel MS08-014 (March 2008)
-CVE-2008-4841 Word MS09-010 (April 2009)
-CVE-2009-0238 Excel MS09-009 (April 2009)
-CVE-2009-0556 Powerpoint MS09-017 (May 2009)
Generic OLESS Format
-FAT FS: SectorNumbers, OLESS directory entries
-Data is divided into directories (storages) and files (streams)
-Depending on the application streams may contain: Macros, Graphics, Tables, Sounds, Animations, etc.
-Parsing can be done using the Win32 COM API: StgOpenStorage(), IStoragemethods, IStreammethods.
Malicious Document Structure
Typical MS-Office Shellcode Behavior
When a bug in a MS Office application gets triggered:
-Finds itself by open file handles enumeration and file size checking
-SetFilePointerto encrypted PE-File(s), decrypt, drop and execute
-Drop harmless embedded MS Office document and start to look innocent
-Not much public information about MS-Office malware analysis available
-Microsoft Office Binary File Format Specification (since Feb. 2008)
-Bruce Dang's talk "Methods for Understanding Targeted Attacks with Office Documents".
Available Tools For Analysis
-DFView (old school Microsoft OLE structure viewer)
-Officecat (signature based CLI utility)
-FlexHexEditor (OLE compound viewer)
-OffVis (office binary file format visualization tool)
-OfficeMalScanner (forensic tool for analysts to find malicious traces in MS Office documents)