Security issue- Index.php file permission set to 00

[eluser]OJ[/eluser]
Thanks Guys, after investigation, my host company said, some guy was spamming my site for more than 90 seconds and they decided to shutdown my site. Too bad anyways and they couldn't even send me an email.
I was sure that I didn't share my ftp account with any one. In this case it was the ISP admin that hacked my site. This is an experience anyways but another disadvantage of using the index.php as the entry point.
I was wondering if I could use another file name instead of the popular index.php as the entry point to my site.
I am not sure if it is safe to use the following entry in htaccess as a subsitute to bare index.php

DirectoryIndex safefile.php

Has any one tried it?