What's the reason for changing access permissions?

[nicholas.berkeley]

       Are there important reasons to change the access permissions?  My host: Inmotion hosting, has strongly advised me not to change the permissions of any of my files or folders to 666 or 777.  That doing so would open a backdoor to the server to hackers.   Following their advice I have left the permissions of the ror.xml and sitemap.xml files at 644; and the generator file at 755.  So far I have not noticed any issues with doing this: I was able to generate all of my sitemaps and submit the xml sitemap to google with no problem.?  Thanks.

[XML-Sitemaps Support]

Hello,

in case if your server allows write access without changing permissions, you can leave it as is. Otherwise generator script will not be able to write sitemap in file.

[nicholas.berkeley]

Thanks  for all of your timely replies to my queries.