Hello Readers my name is Muzamil Hussain.Today I.m gonna tell you. How Can We Block Common Web Attacks And Protect Our Website .On this post i am telling about five types of common web attacks, which are used in
most types of defacements or dumps of databases.
The five exploits listed above are SQL injection, XSS, RCE, RFI, and LFI. Most of the
time, we missed out some website code tags..
coz of this we get website attacks and allows the hacker for attack on vulnerable website.
A: SQL Injection
-->Types
Login Form Bypassing
UNION SQL Injection
B: Cross Site Scripting
--> Cross Site Request Forgery
C: File Inclusion
Types-> Remote File Inclusion and Remote Code Execution
A: SQL Injection
--> LOGIN FORM BYPASSING
Here is an example of the vulnerable code that we can bypass very easily:
index.html file:
<form action="login.php" method="POST" />
<p>Password: <input type="text" name="pass" /><br />
<input type="submit" value="Authenticate" /></p>
</form>
login.php file:
<?php
// EXAMPLE CODE
$execute = "SELECT * from database WHERE password = '{$_POST['pass'])";
$result = mysql_query($execute);
?>
We can simply bypass this by using ' or '1=1', which will execute "password = ''or '1=1'';".
Alternatively, the user can also delete the database by executing "' drop table database; --".
PREVENTION:
Use mysql_real_escape_string in your php code.
Example:
<?php
$badword = "' OR 1 '";
$badword = mysql_real_escape_string($badword);
$message = "SELECT * from database WHERE password = "'$badword'";
echo "Blocked " . $message . ";
?>
--> UNION SQL Injection
UNION SQL injection is when the user uses the UNION command. The user checks for the vulnerability by
adding a tick to the end of a ".php?id=" file. If it comes back with a MySQL error, the site is most likely
vulnerable to UNION SQL injection. They proceed to use ORDER BY to find the columns, and at the end, they use
the UNION ALL SELECT command. An example is shown below.
http://www.site.com/website.php?id=1'
You have an error in your SQL syntax near '' at line 1 SELECT SUM(quantity)
as type FROM orders where (status='completed' OR status='confirmed' OR status='pending') AND user_id=1'
No error--> http://www.site.com/website.php?id=1 ORDER BY 1--
Two columns, and it comes back with an error! This means that there is one column.
http://www.site.com/website.php?id=1 ORDER BY 2--
Selects the all the columns and executes the version() command on the only column.
http://www.site.com/website.php?id=-1 UNION SELECT ALL version()--
SOLUTION:
Add something like below to prevent UNION SQL injection.
$evil = "(delete)|(update)|(union)|(insert)|(drop)|(http)|(--)|(/*)|(select)";
$patch = eregi_replace($evil, "", $patch);
B: Cross Site Scripting
Cross site scripting is a type of vulnerability used by hackers to inject code into vulnerable web pages.
If a site is vulnerable to cross site scripting, most likely users will try to inject the site with malicious javascript or try to
scam users by creating a form where users have to type their information in.
Two types of XSS (cross site scripting) are persistent XSS and non-persistent XSS.
Example:
http://www.site.com/search.php?q=">
SOLUTION:
(javascript) (Thank you, Microsoft!):
function RemoveBad(strTemp) {
strTemp = strTemp.replace(/\<|\>|\"|\'|\%|\;|\(|\)|\&|\+|\-/g,"");
return strTemp;
}
C: File Inclusion
Types: Remote File Inclusion/Local File Inclusion, and Remote Code Execution
Remote File Inclusion allows a hacker to include a remote file through a script (usually PHP). This code is mostly patched on websites, but some websites are still
vulnerable to the vulnerability. RFI usually leads to remote code execution or javascript execution.
Example of the vulnerable code:
<?php
include($_GET['page']);
?>
Exploiting it would be something like this:
http://www.site.com/page.php?page=../../../../../etc/passwd or
http://www.site.com/page.php?page=http://www.site.com/xyz.txt?
SOLUTION:
Validate the input.
$page = $_GET['page'];
$allowed = array('index.php', 'games.php' 'ip.php');
$iplogger = ('ip.php');
if (in_array $page, $pages)) {
include $page {
else
{
include $iplogger
die("IP logged.");
}
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For remote code execution, the site would have to have a php executing command. You would patch this by about doing the same thing.
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