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Security

SQL Injection

SQL Injection :- What, Why & How

1) What is SQL Injection.

2) Why It is happening (Forms of vulnerability)

3) How to prevent it?

 

1) What Is  SQL Injection

SQL injection is a code injection technique that exploits a security vulnerability occurring in the database layer of an application. The vulnerability is present when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and thereby unexpectedly executed. It is an instance of a more general class of vulnerabilities that can occur whenever one programming or scripting language is embedded inside another. SQL injection attacks are also known as SQL insertion attacks.

2) Forms of vulnerability

  • Incorrectly filtered escape characters

This form of SQL injection occurs when user input is not filtered for escape characters and is then passed into an SQL statement. This results in the potential manipulation of the statements performed on the database by the end user of the application.

The following line of code illustrates this vulnerability:

statement = "SELECT * FROM users WHERE name = '" + userName + "';"

This SQL code is designed to pull up the records of the specified username from its table of users. However, if the “userName” variable is crafted in a specific way by a malicious user, the SQL statement may do more than the code author intended. For example, setting the “userName” variable as

' or '1'='1

Or using comments to even block the rest of the query:

' or '1'='1';/*'

renders this SQL statement by the parent language:

SELECT * FROM users WHERE name = '' OR '1'='1';

If this code were to be used in an authentication procedure then this example could be used to force the selection of a valid username because the evaluation of ‘1’=’1′ is always true.

The following value of “userName” in the statement below would cause the deletion of the “users” table as well as the selection of all data from the “userinfo” table (in essence revealing the information of every user), using an API that allows multiple statements:

a';DROP TABLE users; SELECT * FROM userinfo WHERE 't' = 't

This input renders the final SQL statement as follows:

SELECT * FROM users WHERE name = 'a';DROP TABLE users; SELECT * FROM userinfo WHERE 't' = 't';

While most SQL server implementations allow multiple statements to be executed with one call in this way, some SQL APIs such as PHP’s mysql_query() do not allow this for security reasons. This prevents attackers from injecting entirely separate queries, but doesn’t stop them from modifying queries.

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Gumblar Virus

Gumblar Virus: Symptoms, Removal & Prevention.

Symptoms of Gumblar Virus

Your website in getting infected with unknown iframe or scripts and website is getting redirect to any infected website and due to which virus are getting downloaded in your machine.

HOW?

Activity at user End

Visitors to an infected site will be redirected to an alternative site containing further Malware, which was once gumblar.cn, but has now switched to a variety of domains. The site sends the visitor an infected PDF that is opened by the visitor’s browser or Acrobat Reader. The PDF will then exploit a known vulnerability in Acrobat to gain access to the user’s computer. It sometimes also downloads some infected javascript files in the temporary internet folder of the victim’s computer.

The virus will find FTP clients such as FileZilla and Dreamweaver and download the clients’ stored passwords. It also enabled promiscuous mode on the network card, allowing it to sniff local network traffic for FTP details. It is one of the first viruses to incorporate an automated network sniffer.

Activity at server end

Using passwords obtained from site admins, the host site will access a website via FTP and infect the website. It will download large portions of the website and inject malicious code into the website’s files before uploading the files back onto the server. The code is inserted into any file that contains a <body> tag, such as HTML, PHP, JavaScript, ASP and ASPx files. The inserted PHP code contains base64-encoded JavaScript that will infect computers that execute the code. In addition, some pages may have inline frames inserted into them. Typically, iframe code contains hidden links to certain malicious websites. The virus will also modify .htaccess and HOSTS files, and create images.php files in directories named ‘images’. The infection is not a server-wide exploit. It will only infect sites on the server that it has passwords to.

Removal :-

Read More »Gumblar Virus

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