Conduct search engine discovery/reconnaissance for information leakage (OTG-INFO-001)

OWASP Testing Guide v3 Table of Contents

This article is part of the OWASP Testing Guide v3. The entire OWASP Testing Guide v3 can be downloaded here.

OWASP at the moment is working at the OWASP Testing Guide v4: you can browse the Guide here

This is a draft of a section of the new Testing Guide v3

Brief Summary

This section describes how to search the Google Index and remove the associated web content from the Google Cache.

Description of the Issue

Once GoogleBot has completed crawling, it commences indexing the web page based on tags and associated attributes, such as <TITLE>, in order to return the relevant search results. [1]

If the robots.txt file is not updated during the lifetime of the web site, then it is possible for web content not intended to be included in Google's Search Results to be returned.

Therefore, it must be removed from the Google Cache.

Black Box Testing

Using the advanced "site:" search operator, it is possible to restrict Search Results to a specific domain [2].

Google provides the Advanced "cache:" search operator, but this is the equivalent to clicking the "Cached" link of individual Google Search Results. Hence, the use of the Advanced "site:" Search Operator and then clicking the "Cached" link is advocated.

The Google SOAP Search API provides the doGetCachedPage and the associated doGetCachedPageResponse SOAP Messages to assist with archiving the cached pages, if required [3].

Example

To find the web content of owasp.org indexed by Google Cache the following Google Search Query is issued:

site:owasp.org

To display the index.html of owasp.org as cached by Google the following Google Search Query is issued:

cache:owasp.org

Remediation

For urgent removal, Google provide the "URL Removal" function as part of their "Google Webmaster Tools" service [4].

Please note that this still requires you to modify the robots.txt file within the web root directory to "Disallow:" this content from appearing again in the Google Search Results after 90 days.

Gray Box testing and example

Grey Box testing is the same as Black Box testing above

References

[1] "Google 101: How Google crawls, indexes, and serves the web" - http://www.google.com/support/webmasters/bin/answer.py?answer=70897
[2] "Advanced Google Search Operators" - http://www.google.com/help/operators.html
[3] "Google SOAP Search API" - http://code.google.com/apis/soapsearch/reference.html#1_2
[4] "Preventing content from appearing in Google search results" - http://www.google.com/support/webmasters/bin/topic.py?topic=8459