I know this may sound little incomplete but this is what i read on some linux hardening guide.I dont have any clue on how to remove group's write bit.


I m posting the exact sentence of the hardening guide.
What all system files to be taken care of?

To remove group write permissions try this.

Insert your specific directory where you see "directory"

-rwxrwxr-x filename , I think highlighted bit is group write bit, Using this bit permission bit we can give authorize group members to edit file.

Thanks

Some more information about Linux permissions can be found on various pages on the web, for example this one, covering both the textual and octal representation of permissions. The octal representation is a little more compact than the textual one, and not too difficult to understand, so you should get familiar with it. You'll be using octal representation also if (when) you set umask, which you use to control default permissions when files are created. The difference is that with umask you're setting the mask, not the "direct" representation, so be careful.

you can change the basic permissions by manipulating their corresponding bits. It can be done in numeric format where 1 is to execute, 2 is for write and 4 is for reading. It is too much to type to cover this, UnixAcademy.com has training DVDs that cover it well. Keep in mind that in today's Linuxes, there's also implementation of of ACL (access control list, commands like getfacl, setfacl) for Linux, it is rarely used on a trivial, one user stations, but on servers they are used quite often.