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Re: Google's robots.txt handling
From: "Lehman, Jim" <jim.lehman () interactivedata com>
Date: Tue, 11 Dec 2012 23:23:12 +0000

It is possible to use white listing for robots.txt. Allow what you want google to index and deny everything else. That 
way google doesn't make you a goole dork target and someone browsing to your robots.txt file doesn't glean any 
sensitive files or folders. But this will not stop directory bruting to discover your publicly exposed sensitive data, 
that probably should not be exposed to the web in the first place. 

I would rather have some one pound on my server to find something, I might have more time to respond, rather than 
having mr. bad googleing for the weakness in the web site and only making one request to get what they are after.

http://www.sans.org/reading_room/whitepapers/awareness/robotstxt_33955
Its not a great  paper, but it might have some value for those that have not looked into how this file works. 


-----Original Message-----
From: full-disclosure-bounces () lists grok org uk [mailto:full-disclosure-bounces () lists grok org uk] On Behalf Of 
Hurgel Bumpf
Sent: Monday, December 10, 2012 11:26 AM
To: full-disclosure () lists grok org uk
Subject: [Full-disclosure] Google's robots.txt handling

Hi list,


i tried to contact google, but as they didn't answer my email,  i do forward this to FD.
This "security" feature is not cleary a google vulnerability, but exposes websites informations that are not really 
intended to be public.

(Additionally i have to say that i advocate robots.txt files without sensitive content and working security mechanisms.)

Here is an example: 

An admin has a public webservice running with folders containing sensitive informations. Enter these folders in his 
robots.txt and "protect" them from the indexing process of spiders. As he doesn't want the /admin/ gui to appear in the 
search results he also puts his /admin in the robots text and finaly makes a backup to the folder /backup.

Nevertheless these folders arent browsable but they might contain f(a)iles with easy to guess namestructures, 
non-encrypted authentications (simple AUTH) , you name it...

Without a robots.txt nobody would know about the existance of these folders, but as some folders might be linked 
somewhere, these folders might appear in search results when not defined in the robots.txt  The admin finds himself in 
a catch-22 situation where he seems to prefer the robots.txt file.

Long story short.

Although google accepts and respects the directives of the robots.txt file, google INDEXES these files. 

This my concern. 

http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fadmin
http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fbackup
http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+Disallow%3A+%2Fpassword

As these searches can be used less for targeted attacks, they more can be used to find victims. 

http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+%2FDisallow%3A+wp-admin
http://www.google.com/search?q=inurl:robots.txt+filetype%3Atxt+%2FDisallow%3A+typo3
<Just be creative>

This shouldn't be a discussion about bad practice but the google feature itself. 

Indexing a file which is used to prevent indexing.. isn't that just paradox and hypocrite?

Thanks,


Conan the bavarian

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