CentOS against hackers a few small steps

A lot of people are learning Linux operating systems, when when we used Linux operating system Internet, hacker attacks may be encountered, we introduce you some practical tips to prevent hackers under the Linux operating system.
Linux is a multiuser system, once they get to your root user, he can do anything on your system, as the user has full control permissions on the system, if improper operation of or access to, the consequences would be disastrous, how to prevent entry, single user, there are several aspects of.
1, to protect the/etc/inittab file, if you change the 3 in 1 ID:3:initdefault, you can boot directly into single user mode. /Etc/inittab file to root entered by other users cannot modify the rows property is set to.
2, if you are using LILO to boot, possibly through linuxconf or by directly modifying the lilo.conf waiting for input when time is set to 0 or the shortest line. In that case, if entering single user mode, you can use the boot floppy disk.
3, if you use GRUB to boot, the simplest method is to use a GRUB password, to protect the boot options.
4, in order to prevent the remote destruction of others, allowing the system to restart, in addition to the ROOT password, and effective management of files under the/etc directory, the CMOS password should also be set, so that even if the system to single user mode, unable to directly boot the computer to operate.
So that you learn some practical tips to prevent hackers under the Linux operating system, better Internet access through.