Introduction
Web exploitation is the attacking and taking advantage of a vulnerability in a computer system through a web application. There are numerous ways to exploit vulnerabilities so only some of the basics will be covered here. The topics covered in this series can be dangerous enough to compromize an HTTP server's database, code, or allow a remote shell.
Many web sites run web applications for the purpose of dynamic content. Usually this would include an SQL database backend of some sort, and a web application (like forums, talkboards, content management systems, and blogs) to interface with the SQL database. Therefore the affected languages are anything that can be used as an interface over HTTP to dynamic content.
When penetration testing a site, it is different than penetration testing a network, and different than penetration testing a server. However, it is good to point out, that by compromising one of these layers, the other layers can be compromised in the future. Web application vulnerabilities are currently the most prominent vulnerabilities exploited by cybercriminals.
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Exploiting these vulnerabilities against targets which you do not own without written authorization could criminalize you in many countries and most likely the one you live in.
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Affected Languages
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Any CGI interfaced language may also be vulnerable to web exploitation.
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Types of Exploitation
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File inclusion vulnerabilities can be exploited to create a remote shell, which can lead to database manipulation and file tampering.
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Command injection effectively hands a remote shell to an attacker by arbitrary bash or MS-DOS command execution.
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CSRF allows an attacker to perform actions as any unsuspecting user that clicks a link or loads a page on a separate domain from the affected site while logged into the affected site.
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XSCF Sends different data to different hosts. This way, if a piece of malware is able to recognize the source machine as something analyzing it, the malware can return something innocent while normal users are directed to something malicious.
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XSRF is using XSS to produce a same-domain URL that will perform actions as the logged in user via a CSRF attack.
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Mass assignment abuse can allow an attacker to directly overwrite database values without having to write any SQL queries and without the use of SQL injection.
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Attack Vectors
- HTTP GET request parameters (Variables in the URL)
Notice: Rewritten or "clean" URL's can have GET parameters too!
HTTP HEAD requests can also exploit poor input sanitizing in these parameters.
- HTTP POST request parameters (Fields and fieldsets in web forms)
Notice: You can send post parameters to a URL that has GET parameters!
- HTTP Header parameters (Variables passed by header information)
Notice: This includes cookies, user agents, connection type, and more
Fingerprinting
Because web vulnerability identification sometimes requires that you identify the backbone of a particular web configuration, fingerprinting is commonly used as a medium to gain information about commonly used platforms in an attempt to identify them through common fingerprints.
These might include things such as common headers, footers, comments in code- or simply the existence of a very particular page. Fingerprinting is a key aspect in determining vulnerabilities in specific software packages, and might also be used in conjunction with a search engine in order to get large lists of vulnerable hosts through searching for a single commonality.
Tools
In House:
Third party:
Web Exploitation is part of a series on
exploitation.
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