Iptables is not sending LOG to syslog file

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Q. I am running SSH/MySQL/Webserver and setup iptables based firewall. But my logs are send to console rather than the system log files. How do make sure that iptables LOG target messages are send to /var/log/messages file?

A. IPTABLES LOG module turns on kernel logging of matching packets. When this option is set for a rule, the Linux kernel will print some information on all matching packets (like most IP header fields) via the kernel log where it can be read with
dmesg or syslogd.

You can configure level of logging with an option called –log-level level. For example, drop and LOG all incoming port 22 TCP, message:
iptables -I OUTPUT -j LOG --log-level crit -p tcp --dport 22

Read man pages of iptables and syslog.conf for more info.

Restrict ssh access using Iptable

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Q. How do I stop or restrict access to my OpenSSH (SSHD) server using Linux iptables based firewall?

A. Linux iptables firewall can be use to block or restrict access to ssh server. Iptables command is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. However, you can also use tcpd, access control facility for internet services.

Use iptables to Restrict ssh access

Following is simple rule that block all incoming ssh access at port 22
iptables -A INPUT -p tcp -s 0/0 --sport 513:65535 -d 195.55.55.78 --dport 22 -m state --state NEW,ESTABLISHED -j DROP

However in real life you need to use something as follows. Let us assume that your ssh server IP address is 195.55.55.78, remember ssh server use TCP port 22 for all incoming connection. With iptables you can block all incoming connection at port 22 with following two rules:

iptables -A INPUT -p tcp -s 0/0 --sport 513:65535 -d 195.55.55.78 --dport 22 -m state --state NEW,ESTABLISHED -j DROP
iptables -A OUTPUT -p tcp -s 195.55.55.78 --sport 22 -d 0/0 --dport 513:65535 -m state --state ESTABLISHED -j DROP

If you just want to deny access to group of IPS then you need to add following rules to your script:
IPS="202.54.1.20 64.66.44.22 64.66.44.25"
for i in $IPS
do
iptables -A INPUT -p tcp -s 0/0 -s $i --sport 513:65535 -d 195.55.55.78 --dport 22 -m state --state NEW,ESTABLISHED -j DROP
iptables -A OUTPUT -p tcp -s 195.55.55.78 --sport 22 -d $i --dport 513:65535 -m state --state ESTABLISHED -j DROP
done

Add all of above rules to your iptables firewall shell script (do not type @ shell prompt)

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