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Centos and Oracle Linux 6 Server Hardening

Computer security is once again becoming a hot topic for administrators. There are dozens of new sites springing up around the web, and each is slinging their own ‘Perfect’ setup instructions. They have the usual bell curve of good advice, okay advice, and advice that will effectively leave you with a smoldering pile of rubble where your data used to be. Here, we're going to discuss locking down a CentOS 5 system the proper way. This proper way is based on the NSA RHEL5 guide, Steve Grubb's RHEL Hardening presentation, and other reputable sources.

http://wiki.centos.org/HowTos/OS_Protection

 

 

Best Network Security Linux Distros

7 Best Network Security Linux Distributions: On our previous posts, we have featured several Linux distributions specifically made for hard drive data recovery and for web servers. Today, we would like to share with you another list of special purpose distros. These distributions are mainly designed to perform network security tasks such as vulnerability assessment and penetration testing in order to prevent and monitor unauthorized entry, abuse, alteration, or denial of computer network resources. Since most of these distros are available as Live CDs, you could instantly try or use them without hard disk installation.

Here are some of the best Linux distributions (in no particular order) specially made for securing computer networks:

BackTrack

User and Group Permissions

 

OK, fire up your Linux systems and follow along with me for this user and group administration tutorial. This article is your short course on user and group administration using some commands that you’ve perhaps never seen or used before. User management doesn’t have to induce hair pulling (yours or theirs) nor does it have to make you hate user’s existence. Following a single, simple rule will make your life as a system administrator easier: Give your users access to what they need, no more and no less.

Any salty system administrator (SA) will tell you that you’re supposed to manage users with group permissions, and that’s true, but you still have to create those users, place them into groups, remove users and manage user access. It is these basic user management activities that you’ll explore in this week’s post.

Delete Files Older Than x Days on Linux

 

 

The find utility on linux allows you to pass in a bunch of interesting arguments, including one to execute another command on each file. We’ll use this in order to figure out what files are older than a certain number of days, and then use the rm command to delete them.

 

Command Syntax

Finding Directory Sizes in Linux

 

Debian and Ubuntu NTP Time Synchronisation

 

This page describes methods for keeping your computer's time accurate. This is useful for servers, but is not necessary (or desirable) for desktop machines.

NTP is a TCP/IP protocol for synchronising time over a network. Basically a client requests the current time from a server, and uses it to set its own clock.

Centos Samba Share Mounting

 


 This can be made easy by mounting Windows shares on the server. You will be accessing Windows files as if they are local and essentially all Linux commands can be used. Mounting Windows (or other samba) shares is done through the cifs virtual file system client (cifs vfs) implemented in kernel and a mount helpermount.cifs which is part of the samba suite.

The following names are used in our examples.

Setting up SMTP Relay on Ubuntu

 

 I spent some time this afternoon researching what was required to have my servers authenticate to my gmail account and send me the mail that way.  This setup assumes Ubuntu 8.04 (or later) and Postfix.

Install the required packages