Testing: Spidering and googling
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 section describes how to retrieve information about the application being tested using spidering and googling techniques.
Description of the Issue
Web spiders are the most powerful and useful tools developed for both good and bad intentions on the internet. A spider serves one major function, Data Mining. The way a typical spider (like Google) works is by crawling a web site one page at a time, gathering and storing the relevant information such as email addresses, meta-tags, hidden form data, URL information, links, etc. The spider then crawls all the links in that page, collecting relevant information in each following page, and so on. Before you know it, the spider has crawled thousands of links and pages gathering bits of information and storing it into a database. This web of paths is where the term 'spider' is derived from.
The Google search engine found at http://www.google.com offers many features, including language and document translation; web, image, newsgroups, catalog, and news searches; and more. These features offer obvious benefits to even the most uninitiated web surfer, but these same features offer far more nefarious possibilities to the most malicious Internet users, including hackers, computer criminals, identity thieves, and even terrorists. This article outlines the more harmful applications of the Google search engine, techniques that have collectively been termed "Google Hacking." In 1992, there were about 15,000 web sites, in 2006 the number has exceeded 100 million. What if a simple query to a search engine like Google such as "Hackable Websites w/ Credit Card Information" produced a list of websites that contained customer credit card data of thousands of customers per company? If the attacker is aware of a web application that stores a clear text password file in a directory and wants to gather these targets, then he could search on "intitle:"Index of" .mysql_history" and the search engine will provide him with a list of target systems that may divulge these database usernames and passwords (out of a possible 100 million web sites available). Or perhaps the attacker has a new method to attack a Lotus Notes web server and simply wants to see how many targets are on the internet, he could search on "inurl:domcfg.nsf". Apply the same logic to a worm looking for its new victim.
Black Box testing and example
Description and goal
Our goal is to create a map of the application with all the points of access (gates) to the application. This will be useful for the second active phase of penetration testing. You can use a tool such as wget (powerful and very easy to use) to retrieve all the information published by the application.
The -S option is used to collect the HTTP header of the web requests. The --spider options is used to not download anything since we only want the HTTP header.
wget -S --spider <target>
http://www.<target>/ => `index.html' Resolving www.<target>... 64.xxx.xxx.23, 64.xxx.xxx.24, 64.xxx.xxx.20, ... Connecting to www.<target>|64.xxx.xxx.23|:80... connected. HTTP request sent, awaiting response... HTTP/1.1 200 OK Date: Mon, 10 Sep 2007 00:43:04 GMT Server: Apache Accept-Ranges: bytes Cache-Control: max-age=60, private Expires: Mon, 10 Sep 2007 00:44:01 GMT Vary: Accept-Encoding,User-Agent Content-Type: text/html X-Pad: avoid browser bug Content-Length: 135750 Keep-Alive: timeout=5, max=64 Connection: Keep-Alive Length: 135,750 (133K) [text/html] 200 OK
The -r option is used to collect recursively the web-site's content and the -D option restricts the request only for the specified domain.
wget -r -D <domain> <target>
22:13:55 (15.73 KB/s) - `www.******.org/indice/13' saved  --22:13:55-- http://www.******.org/*****/******** => `www.******.org/*****/********' Connecting to www.******.org[xx.xxx.xxx.xx]:80... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] [ <=> ] 11,308 17.72K/s ...
Description and goal
The scope of this activity is to find information about a single web site published on the internet or to find a specific kind of application such as Webmin or VNC. There are tools available that can assist with this technique, for example googlegath, but it is also possibile to perform this operation manually using Google's web site search facilities. This operation does not require specialist technical skills and is a good way to collect information about a web target.
Useful Google Advanced Search techniques
- Use the plus sign (+) to force a search for an overly common word. Use the minus sign (-) to exclude a term from a search. No spaces follow these signs.
- To search for a phrase, supply the phrase surrounded by double quotes (" ").
- A period (.) serves as a single-character wildcard.
- An asterisk (*) represents any word —- not the completion of a word, as is traditionally used.
Google advanced operators help refine searches. Advanced operators use the following syntax: operator:search_term . Notice that there is no space between the operator, the colon, and the search term. A list of operators and search terms follows:
- The site operator instructs Google to restrict a search to a specific web site or domain. The web site to search must be supplied after the colon.
- The filetype operator instructs Google to search only within the text of a particular type of file. The file type to search must be supplied after the colon. Don't include a period before the file extension.
- The link operator instructs Google to search within hyperlinks for a search term.
- The cache operator displays the version of a web page as it appeared when Google crawled the site. The URL of the site must be supplied after the colon.
- The intitle, allintitle operator instructs Google to search for a term within the title of a document.
- The inurl, allinurl operator instructs Google to search only within the URL (web address) of a document. The search term must follow the colon.
- The info operator instructs Google to search only within the summary information of a site
- The phonebook operator instructs Google to search business or residential phone listing.
- The stocks operator instructs Google to search for stock market information about a company.
- The bphonebook operator instructs Google to search business phone listing only.
The following are a set googling examples (for a complete list look at ):
site:www.xxxxx.ca AND intitle:"index.of" "backup"
The operator site: restricts a search in a specific domain, while the intitle: operator makes it possibile to find the pages that contain "index of backup" as a link title of the Google output.
The AND boolean operator is used to combine more conditions in the same query.
Index of /backup/ Name Last modified Size Description Parent Directory 21-Jul-2004 17:48 -
"Login to Webmin" inurl:10000
The query produces an output with every Webmin authentication interface collected by Google during the spidering process.
site:www.xxxx.org AND filetype:wsdl wsdl
The filetype operator is used to find specific kind of files on the web-site.
How can you prevent Google hacking?
Make sure you are comfortable with sharing everything in your public Web folder with the whole world, because Google will share it, whether you like it or not. Also, in order to prevent attackers from easily figuring out what server software you are running, change the default error messages and other identifiers. Often, when a "404 Not Found" error is detected, servers will return a page like that says something like:
Not Found The requested URL /cgi-bin/xxxxxx was not found on this server. Apache/1.3.27 Server at your web site Port 80
The only information that the legimitate user really needs is a message that says "Page Not found." Restricting the other information will prevent your page from turning up in an attacker's search for a specific flavor of server. Google periodically purges it's cache, but until then your sensitive files are still being offered to the public. If you realize that the search engine has cached files that you want to be unavailable to be viewed you can go to http://www.google.com/remove.html and follow the instructions on how to remove your page, or parts of your page, from their database.
Using a search engine to discover virtual hosts
Live.com, another well-known search engine (see link at the bottom of the page), provides the "ip" operator, which returns all the pages that are known to belong to a certain IP address. This is a very useful technique to find out which virtual hosts are configured on the tested server. For instance, the following query will return all indexed pages belonging to the domain owasp.org:
-  Johnny Long: "Google Hacking" - http://johnny.ihackstuff.com
- Google – http://www.google.com
- Live Search - http://www.live.com
- wget - http://www.gnu.org/software/wget/
- Foundstone SiteDigger - http://www.foundstone.com/index.htm?subnav=resources/navigation.htm&subcontent=/resources/proddesc/sitedigger.htm
- NTOInsight - http://www.ntobjectives.com/freeware/index.php
- Burp Spider - http://portswigger.net/spider/
- Wikto - http://www.sensepost.com/research/wikto/
- Googlegath - http://www.nothink.org/perl/googlegath/
- Advanced Dork (Firefox Add-on) - https://addons.mozilla.org/firefox/2144/