How to analyze Squid logs with SARG log analyzer on CentOS

In a previous tutorial, we show how to configure a transparent proxy with Squid on CentOS. Squid provides many useful features, but analyzing a raw Squid log file is not straightfoward. For example, how could you analyze the time stamps and the number of hits in the following Squid log? 1404788984.429 1162 172.17.1.23 TCP_MISS/302 436 […]
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How to set up two-factor authentication for SSH login on Linux

With many high-profile password leaks nowadays, there is a lot of buzz in the industry on “multi-factor” authentication. In a multi-factor authentication system, users are required to go through two distinct authentication procedures: providing something they know (e.g., username/password), and leveraging something they have “physical” access to (e.g., one-time passcode generated by their mobile phone). […]
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How to set up Squid as a transparent web proxy on CentOS or RHEL

In a previous tutorial, we have seen the method of creating a gateway using iptables. This tutorial will focus on turning the gateway into a transparent proxy server. A proxy is called “transparent” when clients are not aware that their requests are processed through the proxy. There are several benefits of using a transparent proxy. […]
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How to set up a secure FTP service with vsftpd on Linux

FTP or File Transfer Protocol is one of the widely used services on the Internet, mainly for transferring files from one host to other. FTP itself was not designed as a secure protocol, and as such, the classic FTP service is vulnerable to common attacks such as man in the middle and brute force attacks. […]
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How to set up Samba as a Primary Domain Controller

A domain controller is a server which groups multiple computers to centralize their authentication system. When you are using a domain controller, you don’t login to your computer, but instead login to the domain controller. Every authentication request is handled by the Primary Domain Controller (PDC). Usually you hear about PDC using a Windows based […]
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How to set up Internet connection sharing with iptables on Linux

In this tutorial, I’ll explain how to share a single Internet connection among multiple devices on Linux. While consumer-grade WiFi routers have become mainstream nowadays, making this problem a non-issue, suppose you don’t have one at home. However, say you have a Linux box already assembled with a modem and a LAN card. The modem […]
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How to monitor Nginx web server from the command line in real time

Once Nginx web server is up and running in a production environment, you will want to monitor its activity in real time. In fact, general network monitoring software such as Nagios, Zabbix, Munin provide support for real-time Nginx monitoring. However, if you do not need comprehensive reporting capabilities or long-term statistics offered by such tools, […]
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