How to hack website using sql injection

SQL Injections or simply called Structured Query Language Injection is a technique that exploits the loop hole in the database layer of the application. This happens when user mistakenly or purposely(hackers) enters the special escape characters into the username password authentication form or in URL of the website. Its called the coding standard loop hole. some website owners doesn't have proper knowledge of secure coding standards and that results into the vulnerable websites. Now assume , you opened a website and went to his Sign in or log in page. Now in username field you have entered something say yogesh and in the password box you pass some escape characters like ',",1=1, etc... Now if the website owner hasn't handled null character strings or escape characters then user will surely get something else that owner never want their users to view.. This is basically called Blind SQL. 

Some basic requirements for sql injection:
1) you need a web browser to open URL and to view source codes.
2) you need notepad++.
3) and very basic  queries of sql like insert , select , update , delete etc.

First of all you can hack those website using SQL injection hacks that allows some input fields from the visitor which can provide input to website like log in page , search page, feedback page etc.
Now a days , HTML pages use POST command to send parameter to another ASP/ASPX page.
Therefore, you may not see the parameter in the URL. You can check the source code of the HTML, and look for "FROM" tag in the HTML code. You may find something like this in some HTML codes:
 
<F O R M action=login.aspx method=post>
<I N P UT type=hidden name=user v a l u e=xyz>
< / F O R M>


Everything between the < F O R M > and < / F O R M > parameters(remove space in words) contains the crucial information and can help us to determine things in more detailed way.

There is alternate method for finding vulnerable website, the websites which have extension ASP, ASPX, JSP, CGI or PHP try to look for the URL's in which parameters are passed. Example is shown below:

http://example.com/login.asp?id=10 

Now how to detect that this URL is vulnerable or not:

Start with single quote trick, take sample parameter as hi'or1=1--. Now in the above URL id is the parameter and 10 is its value. So when we pass hi'or1=1-- as parameter the URL will look like this:

http://example.com/login.asp?id=hi' or 1=1--

You can also do this with hidden field, for that you need to save the webpage and had to made changes to URL and parameters field and modify it accordingly. For example: 

< F O R M action=http://example.com/login. asp method=p o s t >
< i n p u t  type=hidden name=abc value="hi' or 1=1--">
< / F O R M >

 If your luck is favoring you, you will get the login into the website without any username or password.

                                 

But why ' or 1=1-- ?
Take an asp page that will link you to another page with the following URL:

http://example.com/search.asp?category=sports

In this URL 'category' is the variable name and 'sports' is it's value.

Here this request fires following query on the database in background.

SELECT * FROM TABLE-NAME WHERE category='sports'

Where 'TABLE-NAME' is the name of table which is already present in some database.
So, this query returns all the possible entries from table 'search' which comes under the category 'sports'.

Now, assume that we change the URL into something like this:

http://example.com/search.asp?category=sports' or 1=1--

Now, our variable 'category' equals to "sports' or 1=1-- ", which fires SQL query on database something like: SELECT * FROM search WHERE category='sports' or 1=1--'
 

The query should now select everything from the 'search' table regardless if category is equal to 'sports' or not.
A double dash "--" tell MS SQL server to ignore the rest of the query, which will get rid of the last hanging single quote (').
Sometimes, it may be possible to replace double dash with single hash "#".

However, if it is not an SQL server, or you simply cannot ignore the rest of the query, you also may try

' or 'a'='a

 
It should return the same result.
Depending on the actual SQL query, you may have to try some of these possibilities:' or 1=1--
" or 1=1--
or 1=1--
' or 'a'='a
" or "a"="a
') or ('a'='a
'or''='