Configserver Firewall and Security (CSF and LFD)
Published: 12-10-2014 | Author: Remy van Elst | Text only version of this article
Table of Contents
This page covers my notes about csf and lfd. csf is an easy SPI iptablesfirewall suite. lfd is the login failure daemon, which scans log files forfailed authentication and blocks the IP's doing that. This page coversinstallation, populair command line options and popular config file options.
On CentOS systems, first install some required Perl packages:
yum -y install perl-libwww-perl.noarch perl-Time-HiRes
tar -xf csf.tgz
Start the installation:
cd csf ./install.sh
If you have a server with Directadmin:
Set some sane defaults:
perl -pi -w -e "s/TESTING = \"1\"/TESTING = \"0\"/" /etc/csf/csf.confperl -pi -w -e "s/SMTP_BLOCK = \"0\"/SMTP_BLOCK = \"1\"/" /etc/csf/csf.confperl -pi -w -e "s/LF_DSHIELD = \"0\"/LF_DSHIELD = \"86400\"/" /etc/csf/csf.confperl -pi -w -e "s/LF_SPAMHAUS = \"0\"/LF_SPAMHAUS = \"86400\"/" /etc/csf/csf.confperl -pi -w -e "s/LF_DIRWATCH = \"300\"/LF_DIRWATCH = \"120\"/" /etc/csf/csf.confperl -pi -w -e "s/LF_DIRWATCH_DISABLE = \"0\"/LF_DIRWATCH_DISABLE = \"1\"/" /etc/csf/csf.confperl -pi -w -e "s/PT_SKIP_HTTP = \"0\"/PT_SKIP_HTTP = \"1\"/" /etc/csf/csf.confperl -pi -w -e "s/PT_USERPROC = \"10\"/PT_USERPROC = \"15\"/" /etc/csf/csf.confperl -pi -w -e "s/CC_DENY = \"\"/CC_DENY = \"CN,KR,HK,IN,ID,MY,NG,PK,RU,SA,TW,SY,AE\"/" /etc/csf/csf.confperl -pi -w -e "s/IGNORE_ALLOW = \"0\"/IGNORE_ALLOW = \"1\"/" /etc/csf/csf.conf
Done. Do note that the IP you installed from has been added to the allow list.
The idea with csf, as with most iptables firewall configurations, is to blockeverything and then allow through only those connections that you want. This isdone in iptables by DROPPING all connections in and out of the server on allprotocols. Then allow traffic in and out from existing connections. Then openports up in and outgoing for both TCP and UDP individually.
csf command line tips
Block an IP from the server
csf -d 192.168.1.2 csf -d 192.168.0/24
Remove an IP from the blocklist
csf -dr 192.168.1.2
Allow an IP
csf -a 172.16.20.1
Do note that when you allow an IP, it will still be blocked by lfd if it startsbrute forcing. See below, "Don't block IP addresses from the allow list withlfd" to see how to disable it.
Search for an IP:
csf -g 192.168.1.2
View Ports listening for external connections and the executables running
Disable csf and lfd
Enable csf and lfd
Mail yourself a general security check of the server
csf -m email@example.com
These can be placed in either csf.allow or csf.deny.
Allow connections over port 443 to a range of IP addresses:
tcp|out|d=443|d=18.104.22.168/27 # csf.allow
Allow SSH from one IP:
tcp|in|d=22|s=22.214.171.124 # csf.allow
Block traffic to port 80 from a specific range:
The syntax for the advanced rules:
tcp/udp|in/out|s/d=port|s/d=ip|u=uidtcp/udp : EITHER tcp OR udp OR icmp protocolin/out : EITHER incoming OR outgoing connectionss/d=port : EITHER source OR destination port number (or ICMP type) (use a _ for a port range, e.g. 2000_3000)s/d=ip : EITHER source OR destination IP addressu/g=UID : EITHER UID or GID of source packet, implies outgoing connections, s/d=IP value is ignored
/etc/csf/csf/csf.conf file is huge and I recommend you read through it.Below I'll highlight some parts of the config I use more often.
Don't block IP addresses from the allow list with lfd
lfd will also block IP addresses listed in the
csf.allow file.Change the following to make
lfd ignore IP addresses on that list.
IGNORE_ALLOW = "1"
Do note that if one of those IP's starts brute forcing the server, they will notbe blocked.
To allow incoming connections to a specific port, edit the following part of theconfig:
# Allow incoming TCP portsTCP_IN = "20,21,22,25,53,80,110,143,443,465,587,993,995,2222"# Allow incoming UDP portsUDP_IN = "20,21,53"
To allow outgoing ports:
# Allow outgoing TCP portsTCP_OUT = "20,21,22,25,53,80,110,113,443,2222"# Allow outgoing UDP ports# To allow outgoing traceroute add 33434:33523 to this list UDP_OUT = "20,21,53,113,123"
Allow incoming / outgoing ping / ICMP
To allow ICMP/ping, in/out, change the following:
# Allow incoming PINGICMP_IN = "1"# Allow outgoing PINGICMP_OUT = "1"
To block it, change it to "0"
Block certain country's
To block all traffic coming from certain country's:
CC_DENY = "CN,KR,HK,IN,ID,MY,NG,PK,RU,SA,TW,SY,AE"
Use the 2 letter ISO code there.
Disable tracking of long running processes
PT_LIMIT = "0"
If that is set to 1 you will receive a lot of mails when process resource usagespikes or they run longer than a minute.
Enable a Web Management UI
To enable the CSF web management UI, without having a controlpanel (likecpanel/directadmin):
UI = "0"UI_PORT = "6666"UI_USER = "username"UI_PASS = "password"
Send an email when a user logs in via ssh
LF_SSH_EMAIL_ALERT = "1"
The emails are sent to
root by default. Change the below line to change that:
Tags: articles, centos, cpanel, csf, debian, directadmin, firewall, iptables, ubuntu
LF_ALERT_TO = "firstname.lastname@example.org"