Host.conf & sysctl.conf Hardening

Host.conf Hardening –Prevents IP spoofing and dns poisoning

The host.conf file resides in /etc/host.conf.
order bind,hosts
multi on
nospoof on

Sysctl.conf Hardening – Prevents syn-flood attacks and other network abuses.



#Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and
# sysctl.conf(5) for more details.

# Disables packet forwarding
net.ipv4.ip_forward=0

# Disables IP source routing
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.lo.accept_source_route = 0
net.ipv4.conf.eth0.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0

# Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians = 0
net.ipv4.conf.lo.log_martians = 0
net.ipv4.conf.eth0.log_martians = 0

# Disables IP source routing
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.lo.accept_source_route = 0
net.ipv4.conf.eth0.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.lo.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0

# Disables the magic-sysrq key
kernel.sysrq = 0

# Decrease the time default value for tcp_fin_timeout connection
net.ipv4.tcp_fin_timeout = 15

# Decrease the time default value for tcp_keepalive_time connection
net.ipv4.tcp_keepalive_time = 1800

# Turn off the tcp_window_scaling
net.ipv4.tcp_window_scaling = 0

# Turn off the tcp_sack
net.ipv4.tcp_sack = 0

# Turn off the tcp_timestamps
net.ipv4.tcp_timestamps = 0

# Enable TCP SYN Cookie Protection
net.ipv4.tcp_syncookies = 1

# Enable ignoring broadcasts request
net.ipv4.icmp_echo_ignore_broadcasts = 1

# Enable bad error message Protection
net.ipv4.icmp_ignore_bogus_error_responses = 1

# Log Spoofed Packets, Source Routed Packets, Redirect Packets
net.ipv4.conf.all.log_martians = 1

# Increases the size of the socket queue (effectively, q0).
net.ipv4.tcp_max_syn_backlog = 1024

# Increase the tcp-time-wait buckets pool size
net.ipv4.tcp_max_tw_buckets = 1440000

# Allowed local port range
net.ipv4.ip_local_port_range = 16384 65536

# Turn on execshield
kernel.exec-shield=1
kernel.randomize_va_space=1

After you make the changes to the file you need to run /sbin/sysctl -p and sysctl -w net.ipv4.route.flush=1 to enable the changes without a reboot.

The rules were taken from: http://ipsysctl-tutorial.frozentux.net/ipsysctl-tutorial.html

SSH Securing – For a better security of ssh connections.

SSH Securing – For a better security of ssh connections.

Disabling Root Login and changing the listening port .

1.create a user for ssh like sshadminz
2.give the user wheel privilage through Whm
3.in /etc/ssh/sshd_config change the entry PermitRootLogin to no
4.in /etc/ssh/sshd_config change the entry #Port to Port xxxx (needed port,make sure that port is open in csf/iprules)
5.restart the sshd service

>ssh sshadminz@***.***.***.*** -p xxxx

Setting an SSH Legal Message

The message is contained within the following file: /etc/motd

ALERT! You are entering a secured area! Your IP and login information
have been recorded. System administration has been notified.

This system is restricted to authorized access only. All activities on
this system are recorded and logged. Unauthorized access will be fully
investigated and reported to the appropriate law enforcement agencies.

SSH In /etc/ssh/sshd_config,

#Protocol 2, 1
should be changed as
Protocol 2
AllowTcpForwarding no

Restart ssh service

# Only allow the following users SSH Access
AllowUsers User1 User2 etc
# Deny access to the following users
DenyUsers admin etc
# Set the timeout period for idle sessions (in seconds)
ClientAliveInterval 300
ClientAliveCountMax 0
# Disable Host-Based Authentication
HostbasedAuthentication no
# Remove ability to login as Root
PermitRootLogin no
# Change the default SSH Port (Not essential but can help uncomment if you want)
#Port 22
#ListenAddress 192.168.1.1
# Consider CHRooting users to their own directories.
# Subsystem sftp internal-sftp
#Match group sftponly
# ChrootDirectory /home/%u
# X11Forwarding no
# AllowTcpForwarding no
# ForceCommand internal-sftp
# Disable empty passwords from login
PermitEmptyPasswords no
# Set your required Log Level (Either INFO or DEBUG)
LogLevel INFO
# Turn on privilege separation
UsePrivilegeSeparation yes
# Prevent the use of insecure home directory and key file permissions
StrictModes yes
# Turn on reverse name checking
VerifyReverseMapping yes
# Do you need port forwarding?
AllowTcpForwarding no
X11Forwarding no
# Specifies whether password authentication is allowed. The default is yes.
PasswordAuthentication no

CSF AND BFD install

APF or CSF – A policy based iptables firewall system used for the easy configuration of iptables rules.

cd /usr/local/src
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh
echo "CSF successfully installed!"
When your configuration is complete, you need to set the following in /etc/csf/csf.conf to disable “TESTING” mode and enable your firewall:
TESTING = “1″
to
TESTING = “0″

Brute Force Detection – BFD is a shell script for parsing applicable logs and checking for authentication failures and blocks the attackers ip in the firewall

cd /usr/local/src
wget http://www.rfxn.com/downloads/bfd-current.tar.gz
tar -xvzf bfd-current.tar.gz
cd bfd-1.4
./install.sh
echo -e "Please enter your email:"
read email
echo "You entered: $email"
echo "ALERT_USR="1"" >> /usr/local/bfd/conf.bfd
echo "EMAIL_USR="$email"" >> /usr/local/bfd/conf.bfd
echo "Brute Force Detection has been installed!"
echo "Email would be sent to $email"
/usr/local/sbin/bfd -s