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Security Threats
• Cross-site scripting
• SQL injection
• Denial-of-service attack
• Brute Force attack
• Remote file inclusion
• Man in Middle Attack
• Other Server side Threats.

Cross-site scripting(XSS)
• Allows attackers to inject their own malicious
scripts onto web pages and have it executed by
the user’s browser
• Vulnerability commonly seen in :
– Search results that display back the text that was
entered
– Error messages that display the text that caused the
error
– Forms which are filled out whose values are later
displayed to the user
– Web message boards where users can post messages

Defense tactics
Write an HTMLEncode

SQL Injection
• The process of attacker adding his own SQL Statements
in user input
• Used by attackers to
– Gain confidential information (Credit Card numbers,
Account details etc.)
– Bypass authorization
– Perform unauthorized updates
• Injection occurs through :
– Input fields (e.g. UserID and Password entry)
– Query string (values added to website’s URL)
– Manipulated values in HTML

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UserID: Test
Password : 123
Select * from Users where UserID = ‘Test’ and Password = ‘123’;
Web Applications take user input and build an SQL statement which they
send to the database
Drop example

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UserID: Test; drop table users; --
Password : 123
Select * from Users where UserID = ‘Test’; drop table users; -- and Password = ‘123’;
Web Applications take user input and build an SQL statement which they
send to the database

SQL Injection Defense
• It is quite simple: input validation
• Check all input
• Web Applications should not directly build SQL
statements based on user input

Brute Force Attack
• A brute force attack is a trial-and-error method used to
obtain information such as a user password or personal
identification number (PIN).
• In a brute force attack, automated software is used to
generate a large number of consecutive guesses as to
the value of the desired data. Brute force attacks may
be used by criminals to crack encrypted data, or by
security analysts to test an organization's network
security.
A brute force attack may also be referred to as brute
force cracking.

Preventing Brute Force Attack
• Implement an account lockout policy
• Another technique is to use a challenge-
response test to prevent automated
submissions of the login page. Tools such as
the free reCAPTCHA
• Web application should enforce the use
of strong passwords

Dos and DDOS
• Attempt to make a machine or network
resource unavailable to its intended users.
• One common method of attack involves
saturating the target machine with external
communications requests
• attacks usually lead to a server overload

Effects of DDOS
• Consumption of computational resources, such as
bandwidth, memory, disk space,
or processor time.
• Disruption of configuration information, such
as routing information.
• Disruption of state information, such as
unsolicited resetting of TCP sessions.
• Disruption of physical network components.
• Obstructing the communication media between
the intended users and the victim so that they
can no longer communicate adequately.

DDOS Prevention
• An effective defense against an HTTP flood can
be the deployment of a reverse proxy
• increase the capability of the system.
• Load-balancing tools can distribute requests
among many servers scattered across a wide
geographical area

Remote file inclusion
• It allows an attacker to include a file, usually
through a script on the web server.
• vulnerability occurs due to the use of user-
supplied input without proper validation

This can lead to
• Code execution on the web server
• Code execution on the client-side such
as JavaScript which can lead to other attacks
such as cross site scripting (XSS)
• Denial of service (DoS)
• Data theft/manipulation

Prevention
• This type of attack can be defended against at
the .htaccess level and by filtering the inputs.
• Make sure you keep the Global Registers OFF.
This is a biggie that will prevent much evil!
• Hardening the Server

Man in Middle Attack
• A man-in-the-middle attack is a type of
cyberattack where a malicious actor inserts
him/herself into a conversation between two
parties,
• A MITM attack exploits the real-time
processing of transactions, conversations or
transfer of other data.

Prevention
• use a strong encryption between the client
and the server
• you can use a browser plug-in such as HTTPS
Everywhere or ForceTLS.

Server Hardening
• Shut down unused Services
• Hide Services with Port Knocking
– Example:
• Web Server Service is public
• hide SFTP-, SSH- Services
• Use Onetime Passwords by generating them with
Password generators
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Restrict Resources to avoid DoS-Attacks
• Change Default TimeOut
• Restrict HTTP-Requests
Restrict access to Web Resources
• Often resources are not to be accessible for everyone
• htaccess is a simple mechanism for access Protection
• htaccess is activated by a file .htaccess to protected
directory (or above in one)
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Source: http://www.howtomonster.com/2007/08/12/how-to-restrict-access-to-a-web-site-folder/

Linux Systems Monitoring Cycle
28

OWASP
• The Open Web Application Security Project is
an online community dedicated to web
application security. The OWASP community
includes corporations, educational
organizations, and individuals from around the
world
• https://www.owasp.org/

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