Find files that are not world readable and make them readable:
sudo find . -type f \! -perm -4 -exec chmod o+r {} +
Find files that are not group readable
find . -type f \! -perm -40 -ls
Find files that are group writable
find . -type f -perm -20 -ls
Find files that are world writable
find . -type f -perm -2 -ls