Iptables Anti DDos config

# AntiPort scan
-A INPUT -m state --state NEW -p tcp --tcp-flags ALL ALL -j DROP
-A INPUT -m state --state NEW -p tcp --tcp-flags ALL NONE -j DROP
# Denie 2 second recent create 6 new connect per ip
 -A INPUT -p tcp -m tcp --dport 80 -m state --state NEW -m recent --set --name DEFAULT --rsource
-A INPUT -p tcp -m tcp --dport 80 -m state --state NEW -m recent --update --seconds 2 --hitcount 6 --name DEFAULT --rsource -j DROP
-A INPUT -p tcp --dport 80 -m limit --limit 3/sec --limit-burst 10 -j DROP
-A INPUT -p tcp --syn --dport 80 -m connlimit --connlimit-above 15 -j DROP
-A INPUT -p tcp -m string --string "string you want to block" --algo bm -j DROP
-A INPUT -p tcp -m string --string "string you want to block" --algo kmp -j DROP
-A INPUT -p tcp -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -s "your IP" -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp --tcp-flags ALL NONE -j DROP
-A INPUT -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP
-A INPUT -p tcp --tcp-flags SYN,RST SYN,RST -j DROP
-A INPUT -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
-A INPUT -p tcp --tcp-flags FIN,RST FIN,RST -j DROP
-A INPUT -p tcp --tcp-flags SYN,ACK SYN,ACK -m state --state NEW -j DROP
-A INPUT -p tcp --tcp-flags ACK,FIN FIN -j DROP
-A INPUT -p tcp --tcp-flags ACK,PSH PSH -j DROP
-A INPUT -p tcp --tcp-flags ACK,URG URG -j DROP
-A INPUT -m state --state INVALID -j DROP
-A FORWARD -m state --state INVALID -j DROP
-A OUTPUT -m state --state INVALID -j DROP
-A INPUT -p tcp --tcp-flags ALL FIN,PSH,URG -j DROP
-A INPUT -p tcp --tcp-flags ALL SYN,FIN,PSH,URG -j DROP
-A INPUT -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP
-A INPUT -p tcp --tcp-flags ACK,FIN FIN -j DROP
-A INPUT -p tcp --tcp-flags RST RST -j DROP
-A INPUT -p tcp ! --syn -m state --state NEW -j DROP
-A INPUT -m conntrack --ctstate NEW -p tcp --tcp-flags ALL ACK,RST,SYN,FIN -j DROP
#-A INPUT -m conntrack --ctstate NEW -p tcp --tcp-flags SYN,RST,ACK,FIN,URG,PSH SYN -j DROP
-A INPUT -m conntrack --ctstate NEW -p tcp --tcp-flags SYN,RST,ACK,FIN,URG,PSH FIN -j DROP
-A INPUT -m conntrack --ctstate NEW -p tcp --tcp-flags SYN,RST,ACK,FIN,URG,PSH ACK -j DROP
-A INPUT -m conntrack --ctstate INVALID -p tcp --tcp-flags ! SYN,RST,ACK,FIN,URG,PSH SYN,RST,ACK,FIN,URG,PSH -j DROP
-A INPUT -m conntrack --ctstate NEW -p tcp --tcp-flags SYN,RST,ACK,FIN,URG,PSH FIN,URG,PSH -j DROP
# Now allow for HTTP
-A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p icmp -m icmp --icmp-type any -j ACCEPT
-A INPUT -p tcp --syn -j DROP
-A INPUT -j REJECT
-A FORWARD -j REJECT

Fixing postfix and saslauthd: cannot connect to saslauthd

If you are having issues getting postfix email server to authenticate with saslauthd, your solution might be found in a missing symlink.  Remember that postifx runs in a chroot environment.
I find the following warning message in /var/log/mail.log:

 warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory

The warning message tells me that saslauthd can’t be located. The real location is /var/spool/postfix/var/run/saslauthd, but postfix is expecting to find it in /var/run/saslauthd.  Create a symlink as described below and see if that fixes your problem.

sudo ln -s /var/spool/postfix/var/run/saslauthd /var/run
sudo chown root:sasl /var/spool/postfix/var/run/saslauthd
sudo usermod -a -G sasl postfix

Be sure to restart postfix and saslauthd.

sudo /etc/init.d/postfix restart
sudo /etc/init.d/saslauthd restart

After restarting saslauthd, you should see some of the following files in /var/spool/postfix/var/run/saslauthd:

cache.flock cache.mmap mux/ mux.accept saslauthd.pid

Test using your smtp client and verify that you no long receive the previous warning message in your mail.log file.  Hopefully this was your quick fix.

Repo for Centos

For x64

# wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm && wget http://rpms.famillecollet.com/enterprise/remi-release-7.rpm && wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm && rpm -Uvh remi-release-*.rpm epel-release-*.noarch.rpm rpmforge-release-*.rpm

and x86...

# wget http://dl.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm && wget http://rpms.famillecollet.com/enterprise/remi-release-5.rpm && wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el5.rf.x86_64.rpm && rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm rpmforge-release-*.rpm

for both of them.

wget -q -O - http://www.atomicorp.com/installers/atomic |sh