Databases, Systems & Networks

According to the official project site:

netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.

This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. I strongly recommend that you first read our quick tutorial that explains how to configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux. This post lists most simple iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders. Lire la suite…

The purpose of this post is to introduce a user to the nmap command line tool to scan a host and/or network, so to find out the possible vulnerable points in the hosts. You will also learn how to use Nmap for offensive and defensive purposes.

nmap in action

More about nmap

From the man page:

Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.

It was originally written by Gordon Lyon and it can answer the following questions easily:

1. What computers did you find running on the local network?
2. What IP addresses did you find running on the local network?
3. What is the operating system of your target machine?
4. Find out what ports are open on the machine that you just scanned?
5. Find out if the system is infected with malware or virus.
6. Search for unauthorized servers or network service on your network.
7. Find and remove computers which don’t meet the organization’s minimum level of security.

Lire la suite…

MySQL database is a popular for web applications and acts as the database component of the LAMP, MAMP, and WAMP platforms. Its popularity as a web application is closely tied to the popularity of PHP, which is often combined with MySQL. MySQL is open source database server and by default it listen on TCP port 3306. In this tutorial you will learn how to open TCP port # 3306 using iptables command line tool on Linux operating system.

Task: Open port 3306

In most cases following simple rule opens TCP port 3306:

iptables -A INPUT -i eth0 -p tcp -m tcp --dport 3306 -j ACCEPT

The following iptable rules allows incoming client request (open port 3306) for server IP address 202.54.1.20. Add rules to your iptables shell script:

iptables -A INPUT -p tcp -s 0/0 --sport 1024:65535 -d 202.54.1.20 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 3306 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

However in real life you do not wish give access to everyone. For example in a web hosting company, you need to gives access to MySQL database server from web server only. Following example allows MySQL database server access (202.54.1.20) from Apache web server (202.54.1.50) only:

iptables -A INPUT -p tcp -s 202.54.1.50 --sport 1024:65535 -d 202.54.1.20 --dport 3306 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp -s 202.54.1.20 --sport 3306 -d 202.54.1.50 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

Please note if you follow above setup, then you need tell all your hosting customer to use 202.54.1.50 as MySQL host in PHP/Perl code. A better approach is to create following entry in /etc/hosts file or use fully qualified domain name (create dns entry) mysql.hostingservicecompany.com which points to 202.54.1.50 ip:
202.54.1.50 mysql

In shot MySQL database connection code from PHP hosted on our separate webserver would look like as follows:

// ** MySQL settings ** //
define('DB_NAME', 'YOUR-DATABASE-NAME');     // The name of the database
define('DB_USER', 'YOUR-USER-NAME');     // Your MySQL username
define('DB_PASSWORD', 'YOUR-PASSWORD''); // ...and password
define('DB_HOST', 'mysql');       // mysql i.e. 202.54.1.50
// ** rest of PHP code ** //

Lire la suite…

Source: how-to.ovh

Marre des pays exotiques qui essaient de s’introduire sur le serveur et pourrissent vos logs et font bosser fail2ban ?

Une solution pour bloquer les pays avec lesquels vous n’avez pas de relations. Pour Debian mais sûrement adaptable à d’autres distributions.

# Install GeoIP pour iptables

apt-get install dkms xtables-addons-dkms xtables-addons-common xtables-addons-dkms geoip-database libgeoip1 libtext-csv-xs-perl unzip

# On vérifie que c’est ok

dkms status xtables-addons

# on crée le repertoire

mkdir /usr/share/xt_geoip

# on se déplace dedans

cd /usr/share/xt_geoip/

# on télécharge le fichier

wget http://man.sethuper.com/wp-content/uploads/2013/06/geoip-dl-build.tar.gz

# on le décompresse

tar xvf geoip-dl-build.tar.gz

# on l’exécute

./xt_geoip_dl

# si cela donne un message d’erreur, on fait ceci

/usr/bin/perl -MCPAN -e'install Text::CSV_XS'

# on exécute l’autre fichier

./xt_geoip_build -D . *.csv

# on efface les fichiers inutiles

rm -rf geoip-dl-build.tar.gz

# on teste iptables en bloquant la Chine et la Russie

iptables -A INPUT -m geoip --src-cc CN,RU -j DROP

# on vérifie

iptables -L -v

# ce qui donnera cette ligne indiquant que les pays seront bloqués

DROP all -- anywhere anywhere -m geoip --source-country CN,RU

pour interdire le port 22 à ces pays

iptables -A INPUT -p tcp --dport 22 -m geoip --src-cc CN,RU -j DROP