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John Jackson
John Jackson

Linux Server Hardening


Each time you work on a new Linux hardening job, you need to create a new document that has all the checklist items listed in this post, and you need to check off every item you applied on the system. Furthermore, on the top of the document, you need to include the Linux host information:




Linux Server Hardening


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Another password policy that should be forced is strong passwords. The PAM module offers a pam_cracklib that protects your server from dictionary and brute-force attacks. To accomplish this task, open the file /etc/pam.d/system-auth using any text editor and add the following line:


Telnet and rlogin protocols uses plain text, not encrypted format which is the security breaches. SSH is a secure protocol that use encryption technology during communication with server.


NIC Bonding helps us to avoid single point of failure. In NIC bonding, we bond two or more Network Ethernet Cards together and make one single virtual Interface where we can assign IP address to talk with other servers. Our network will be available in case of one NIC Card is down or unavailable due to any reason.


Implementing secure configurations across your computing environment, including your Unix and Linux systems, is a key security best practice because it reduces your attack surface area and limits the damage that cyberattacks can do. Indeed, system hardening is a core control in many compliance directives.


The most secure Linux server or other computer is the one that is powered off and disconnected from the network. But if we want to actually use the machine to provide IT services, we need to maximize its security defenses when it is booted up and attached to the network or even the internet.


This is where hardening comes into play. Hardening a system means optimizing its configuration for secure operations and data protection. The range of exploitable vulnerabilities is vast, so there are three main rules to follow:


Start by stripping out any features, utilities and services that are not required for running the server. Uninstall unnecessary software and disable system services that are not needed. Since the hardware in your infrastructure also presents exploitable vulnerabilities, make sure any accessible interfaces, such as USB ports, are disabled or even physically removed from the machine.


As the primary route for remotely administering your Linux systems, SSH requires particular attention. There are a number of default settings in the /etc/ssh/sshd_config file that need to be enabled in order to harden the SSH server operation.


For example, the default configuration enables the outdated and less secure version 1 of the SSH protocol. CIS hardening guidance recommends enabling version 2 to enhance security. To do so, simply uncomment the Protocol 2 setting in the configuration file (/etc/ssh/sshd_config) by removing the #, as follows:


A simplified operating system with a reduced footprint is attractive when the full range of function usually provided by server-grade Linux devices is not required and hardware resources such as storage, memory and CPU have been minimized to save manufacturing costs. For example, the open-source Android platform developed by Google is optimized for smart phones and TVs, and the OpenWrt router firmware is used for a wide range of broadband routers.


The functionality included in the operating system varies widely depending upon the intended application. For example, Android includes screen lock, face recognition, PIN entry support and location services; these are not needed in operating systems for home routers, but VPN, guest Wi-Fi and bandwidth throttling features are included. As a result, hardening guidance is specifically linked to the particular device and platform in use.


Similarly for Linux Mint, as an Ubuntu-derived Desktop Linux platform, the same hardening procedures used for Debian-Linux should be adopted. Work through the earlier Linux Hardening Checklist steps and apply these to your Linux Mint systems.


When you perform an inside-looking-around vulnerability assessment, you are at an advantage since you are internal and your status is elevated to trusted. This is the point of view you and your co-workers have once logged on to your systems. You see print servers, file servers, databases, and other resources.