vi /etc/sysconfig/iptables

*filter
:FORWARD DROP [0:0]
:INPUT DROP [0:0]
:OUTPUT DROP [0:0]
 
## Block IPs here
-A INPUT -s xxx.xxx.xxx.xxx -j DROP
 
-A INPUT -i eth0 -f -j DROP
-A INPUT -i lo -j ACCEPT
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG NONE -j DROP
-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,SYN,RST,PSH,ACK,URG -j DROP
-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,PSH,ACK,URG FIN,PSH,URG -j DROP
-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN FIN,SYN -j DROP
-A INPUT -p tcp -m tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A INPUT -p tcp -m tcp --tcp-flags FIN,RST FIN,RST -j DROP
-A INPUT -p tcp -m tcp --tcp-flags FIN,ACK FIN -j DROP
-A INPUT -p tcp -m tcp --tcp-flags PSH,ACK PSH -j DROP
-A INPUT -p tcp -m tcp --tcp-flags ACK,URG URG -j DROP
 
## Open all your needed ports here
-A INPUT -p tcp -m state -m tcp --dport 25 --state NEW -j ACCEPT
-A INPUT -p tcp -m state -m tcp --dport 80 --state NEW -j ACCEPT
 
## Allow your IPs here
-A INPUT -p tcp -m state -m tcp -s xxx.xxx.xxx.xxx/255.255.255.0 --dport 10000 --state NEW -j ACCEPT
 
-A INPUT -p tcp -m tcp -m state ! --tcp-flags FIN,SYN,RST,ACK SYN --state NEW -j DROP
-A INPUT -f -j DROP
-A OUTPUT -o lo -j ACCEPT
-A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -j ACCEPT
-A OUTPUT -p udp -m state --state NEW,ESTABLISHED -j ACCEPT
-A OUTPUT -p icmp -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
COMMIT
 
*nat
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
COMMIT
 
*mangle
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
COMMIT

# 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.
 
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
 
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syncookies = 1
 
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
 
########## IPv6 networking start ##############
# Number of Router Solicitations to send until assuming no routers are present.
# This is host and not router
net.ipv6.conf.default.router_solicitations = 0
 
# Accept Router Preference in RA?
net.ipv6.conf.default.accept_ra_rtr_pref = 0
 
# Learn Prefix Information in Router Advertisement
net.ipv6.conf.default.accept_ra_pinfo = 0
 
# Setting controls whether the system will accept Hop Limit settings from a router advertisement
net.ipv6.conf.default.accept_ra_defrtr = 0
 
#router advertisements can cause the system to assign a global unicast address to an interface
net.ipv6.conf.default.autoconf = 0
 
#how many neighbor solicitations to send out per address?
net.ipv6.conf.default.dad_transmits = 0
 
# How many global unicast IPv6 addresses can be assigned to each interface?
net.ipv6.conf.default.max_addresses = 1
 
########## IPv6 networking ends ##############
 
# Enable ExecShield protection
kernel.exec-shield = 1
kernel.randomize_va_space = 1
 
# increase system file descriptor limit
fs.file-max = 65535
 
# Allow for more PIDs
kernel.pid_max = 65536
 
#Increase system IP port limits
net.ipv4.ip_local_port_range = 11000 65000
 
# Reboot after a kernel panic
kernel.panic = 30