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What is SQL Injection? Can any one explain in detail.


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SQL Injection happens when a developer accepts user input that is directly placed into a SQL Statement and doesn't properly filter out dangerous characters. This can allow an attacker to not only steal data from your database, but also modify and delete it. Certain SQL Servers such as Microsoft SQL Server contain Stored and Extended Procedures (database server functions). If an attacker can obtain access to these Procedures it may be possible to compromise the entire machine. Attackers commonly insert single qoutes into a URL's query string, or into a forms input field to test for SQL Injection. If an attacker receives an error message like the one below there is a good chance that the application is vulnerable to SQL Injection.
SQL injection is a type of security exploit in which the attacker adds Structured Query Language (SQL) code to a Web form input box to gain access to resources or make changes to data. An SQL query is a request for some action to be performed on a database. Typically, on a Web form for user authentication, when a user enters their name and password into the text boxes provided for them, those values are inserted into a SELECT query. If the values entered are found as expected, the user is allowed access; if they aren't found, access is denied. However, most Web forms have no mechanisms in place to block input other than names and passwords. Unless such precautions are taken, an attacker can use the input boxes to send their own request to the database, which could allow them to download the entire database or interact with it in other illicit ways.
The risk of SQL injection exploits is on the rise because of automated tools. In the past, the danger was somewhat limited because an exploit had to be carried out manually: an attacker had to actually type their SQL statement into a text box. However, automated SQL injection programs are now available, and as a result, both the likelihood and the potential damage of an exploit has increased enormously. In an interview with Security Wire Perspectives, Caleb Sima, CTO of SPI Dynamics spoke of the potential danger: "This technology being publicly released by some black hat will give script-kiddies the ability to pick up a freeware tool, point it at a Web site and automatically download a database without any knowledge whatsoever. I think that makes things a lot more critical and severe. The automation of SQL injection gives rise to the possibility of a SQL injection worm, which is very possible. In fact, I am surprised this hasn't occurred yet." Sima estimates that about 60% of Web applications that use dynamic content are vulnerable to SQL injection.
SQL injection is a technique for exploiting web applications that use client-supplied
data in SQL queries without stripping potentially harmful characters first. Despite being
remarkably simple to protect against, there is an astonishing number of production systems
connected to the Internet that are vulnerable to this type of attack. The objective of this paper
is to educate the professional security community on the techniques that can be used to take
advantage of a web application that is vulnerable to SQL injection, and to make clear the
correct mechanisms that should be put in place to protect against SQL injection and input
validation problems in general.
Uses The SQL Injection
1] or a=a--
2] ' or 1=1 or ''='
3] " or 1=1--
4] ') or ('1'='1--
5] ') or '1'='1--
6] ' or 1=1/*
7] ' or 1=1#
8] ' or 1=1--
9] ' or 1=1 or ''='
need to know the expected result of each point and where should i write it ?
SQL injection is a technique used to take advantage of non-validated input vulnerabilities to pass SQL commands through a Web application for execution by a backend database. Attackers take advantage of the fact that programmers often chain together SQL commands with user-provided parameters, and can therefore embed SQL commands inside these parameters. The result is that the attacker can execute arbitrary SQL queries and/or commands on the backend database server through the Web application.


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