To change the owner of a file or a directory type:

#change owner to a file
chown username file

 

#change owner to a directory
chown username directory

To change the group to a file or a directory type:

#change group to a file
chgrp group file

 

#change group to a directory
chgrp group directory

Recursive and Verbose

To change the owner of a directory and of all its content and subfolders, type:

chown -R username directory

You can also use the -v parameter for verbose mode as follow:

chown -Rv username directory

The above parameters are valid also for chgrp, that is used to change group.

CTRL + C

The above command will interrupt the previous started command and will return the shell prompt.

sort file_name

Now show only the unique lines:

sort file_name | uniq

And finally save the unique lines in a new file:

sort file_name | uniq > file_name_uniques

Snort is an open source network intrusion prevention system, capable of performing real-time traffic analysis and packet logging on IP networks. It can perform protocol analysis, content searching/matching, and can be used to detect a variety of attacks and probes, such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, and much more.

IPCop Firewall 1.4.21

IPCop Firewall is a Linux firewall distribution geared towards home and SOHO (Small Office/Home Office) users. The IPCop interface is very user-friendly and task-based. IPCop offers the critical functionality of an expensive network appliance using stock, or even obsolete, hardware and OpenSource Software.
Homepage

Firestarter

Firestarter is an Open Source visual firewall program. The software aims to combine ease of use with powerful features, therefore serving both Linux desktop users and system administrators.
We strongly believe that your job is to make the high level security policy decisions and ours is to take care of the underlying details. This is a departure from your typical Linux firewall, which has traditionally required arcane implementation specific knowledge.
Homepage

Lutel Firewall

LutelWall (formerly known as Lutel Firewall) is high-level linux firewall configuration tool. It uses human-readable and easy to understand configuration to set up Netfilter in most secure way. Its flexibility allows firewall admins build from very simple, single-homed firewalls, to most complex ones – with multiple subnets, DMZ’s and traffic redirections. It can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone system.
Homepage

LEAF – Linux Embedded Appliance Framework

A secure, feature-rich, customizable embedded Linux network appliance for use in a variety of network topologies. Although it can be used in other ways; it’s primarily used as a Internet gateway, router, firewall, and wireless access point.
Homepage

PCX Firewall 2.24

What is the PCXFirewall?
It is a Toolkit of perl libraries that allow you to define firewall rules for the Linux netfilter/iptables subsystem.
Homepage

Shoreline Firewall (Shorewall)

The Shoreline Firewall, more commonly known as “Shorewall”, is a high-level tool for configuring Netfilter. You describe your firewall/gateway requirements using entries in a set of configuration files. Shorewall reads those configuration files and with the help of the iptables utility, Shorewall configures Netfilter to match your requirements. Shorewall can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone GNU/Linux system. Shorewall does not use Netfilter’s ipchains compatibility mode; as a consequence, Shorewall can take advantage of Netfilter’s connection state tracking capabilities to create a stateful firewall.
Homepage

KMyFirewall

KMyFirewall is an IPTables based firewall configuration tool for KDE (the K Desktop Environment) running on Linux based systems.
KMyFirewall attempts to make it easier to setup IPTables based firewalls on Linux systems.
It will be the right tool if you like to have a so called “Personal Firewall” running on your Linux box, but don’t have the time and/or the interest to spend hours in front of the IPTables manual just to setup a firewall that keeps the “bad” people out.
Homepage

Firewall Builder 3.0.1

Firewall Builder is a GUI firewall configuration and management tool that supports iptables (netfilter), ipfilter, pf, ipfw, Cisco PIX (FWSM, ASA) and Cisco routers extended access lists. Firewall Builder uses object-oriented approach, it helps administrator maintain a database of network objects and allows policy editing using simple drag-and-drop operations.
Homepage

DNS Flood Detector 1.12

DNS Flood Detector was developed to detect abusive usage levels on high traffic nameservers and to enable quick response in halting the use of one’s nameserver to facilitate spam.
DNS Flood Detector uses libpcap (in non-promiscuous mode) to monitor incoming dns queries to a nameserver. The tool may be run in one of two modes, either daemon mode or “bindsnap” mode. In daemon mode, the tool will alarm via syslog. In bindsnap mode, the user is able to get near-real-time stats on usage to aid in more detailed troubleshooting.
Homepage

Endian Firewall Community 2.2 RC3

Endian Firewall Community is a “turn-key” linux security distribution that turns every system into a full featured security appliance with Unified Threat Management (UTM) functionality. The software has been de signed with “usability in mind” and is very easy to install, use and manage, without losing its flexibility. The features include a stateful packet inspection firewall, application-level proxies for various protocols (HTTP, FTP, POP3, SMTP) with antivirus support, virus and spamfiltering for email traffic (POP and SMTP), content filtering of Web traffic and a “hassle free” VPN solution (based on OpenVPN). The main advantage of Endian Firewall is that it is a pure “Open Source” solution that is sponsored by Endian.
Homepage

pfSense Open Source Firewall Distribution

pfSense is a free, open source customized distribution of FreeBSD tailored for use as a firewall and router. In addition to being a powerful, flexible firewalling and routing platform, it includes a long list of related features and a package system allowing further expandability without adding bloat and potential security vulnerabilities to the base distribution. pfSense is a popular project with more than 1 million downloads since its inception, and proven in countless installations ranging from small home networks protecting a PC and an Xbox to large corporations, universities and other organizations protecting thousands of network devices.
pfSense includes most all the features in expensive commercial firewalls, and more in many cases. The following is a list of features currently available in the pfSense 1.2 release. All of these things are possible in the web interface, without touching anything at the command line.
Homepage