Penetration testers must be able to think outside of the box and to use whatever method is necessary in order to discover information about their targets.Malicious attackers will not stop in the conventional tactics and this should apply and to the penetration tester.Many organizations are uploading in their websites word documents and excel files without been aware that they expose sensitive information.This information is hidden in the metadata of the files.Also in application assessments (web or mobile) it is a good practice except of the common vulnerabilities to check and the metadata in order to see if this information can be used in a malicious way.In this article we will examine some of the tools that we can use for metadata extraction and what kind of information can unveil.
Exiftool
One of the tools that can extract Metadata information is the exiftool.This tool is found in Backtrack distribution and can extract information from various file types like DOC,XLS,PPT,PNG and JPEG.Typically the information that we would look for are:
- Title
- Subject
- Author
- Comments
- Software
- Company
- Manager
- Hyperlinks
- Current User
Below is the information that we have obtained from an image and the metadata from a doc file.
Extracting metadata of an image – exiftool
Metadata of a doc file
Metadata of a doc file 2
FOCA
FOCA is another great tool for analyzing metadata in documents.It is a GUI based tool which make the process a lot of easier.The only thing that we have to do is to specify the domain that we want to search for files and the file type (doc,xls,pdf) and FOCA will perform the job for us very easily.Below you can see a screenshot of the metadata that we have extracted from a doc file.As you can see we have obtained a username an internal path and the operating system that the file has created.
FOCA – Metadata
Conclusion
As we have seen in this article metadata can unveil important information which can be used in conjunction with other attacks.Companies should be aware about this exposure of information that exist in their documents and before they upload something on public domain must use the appropriate tools first in order to remove the metadata from their files and to mitigate the risk.
Feb 20, 2013 @ 14:52:56
As always, great article, thanks.
Could you give examples as to how the hidden metadata could be used maliciously?
Say for example, am I right in saying a hidden hyperlink url may accidently be linking to an open web address/folder, or an exposed author name could give the pen tester a name to social engineer etc?
Are there any other common uses / examples of metadate being used?
Feb 20, 2013 @ 15:25:37
These data can be used in social engineering attempts as you mentioned correctly but it is not only that.If for example you obtain a user account as the last image indicates then you already have a valid username to play with and you need to discover the password in an infrastructure penetration test.If you find an internal path this is considered an information disclosure vulnerability so you should mention it on your report and you could potentially use this information as soon as you got access to the company’s network in order to discover and other valid paths or network shares.
Feb 07, 2014 @ 22:11:49
Great Article!!!!!!!
Many thanks..
Will be usefull