One may append the comment “–” operator along with the String for the username and whole avoid executing the password segment of the SQL query. Everything when the — operator would be considered as comment and not dead.
To launch such an attack, the value passed for name could be ’OR ‘1’=‘1’ ; —Statement = “SELECT * FROM ‘CustomerDB’ WHERE ‘name’ = ‘ ”+ userName + “ ‘ AND ‘password’ = ‘ ” + passwd + “ ‘ ; ”
Statement = “SELECT * FROM ‘CustomerDB’ WHERE ‘name’ = ‘ ’ OR ‘1’=‘1‘;– + “ ‘ AND ‘password’ = ‘ ” + passwd + “ ‘ ; ”
All the records from the customer database would be listed.
Yet, another variation of the SQL Injection Attack can be conducted in dbms systems that allow multiple SQL injection statements. Here, we will also create use of the vulnerability in sure dbms whereby a user provided field isn’t strongly used in or isn’t checked for sort constraints.
This could take place once a numeric field is to be employed in a SQL statement; but, the programmer makes no checks to validate that the user supplied input is numeric.
Variation is an evasion technique whereby the attacker can easily evade any comparison statement. The attacker does this by placing characters such as “' or '1'='1'” in any basic injection statement such as “or 1=1” or with other accepted SQL comments.
Evasion Technique: Variation Variation is an evasion technique whereby the attacker can easily evade any comparison statement. The attacker does this by placing characters such as “' or '1'='1'” in any basic injection statement such as “or 1=1” or with other accepted SQL comments. The SQL interprets this as a comparison between two strings or characters instead of two numeric values. As the evaluation of two strings yields a true statement, similarly, the evaluation of two numeric values yields a true statement, thus rendering the evaluation of the complete query unaffected. It is also possible to write many other signatures; thus, there are infinite possibilities of variation as well. The main aim of the attacker is to have a WHERE statement that is always evaluated as “true” so that any mathematical or string comparison can be used, where the SQL can perform the same.
