Linux web hosting and server support tips

Tag: block

How to block Outgoing Port 25 for all VPS/Containers of SolusVM

How to block Outgoing Port 25 for all VPS/Containers of SolusVM(Both OpenVZ/KVM)

Sometimes,when providing VPS service, it is necessary to block mailing service for VPS. Otherwise your IP ranges will be blocked by RBLs and other common mail providers like Gmail, Hotmail, AOL, etc. It is recommended to open ports by case by case for your customers, after establishing trust with your client.

Normally we block the port using the “OUTPUT” chain. However, SolusVM uses the chain “FORWARD” for routing traffic from containers/VPSs.

So by adding following rules, you can block all outgoing mails ports completely for all VPSs.

iptables -I FORWARD -d 0.0.0.0/0 -p tcp -m tcp --dport 25 -j DROP
iptables -I FORWARD -d 0.0.0.0/0 -p tcp -m tcp --dport 465 -j DROP
iptables -I FORWARD -d 0.0.0.0/0 -p tcp -m tcp --dport 587 -j DROP

Then save the iptables by running

service iptables save

Disable/suspend email service for one domain – cPanel

Disable/suspend email service for one domain

From version 56, cPanel provides API support to disable email service for domain or email accounts. Please note this limit cannot be override by the user from their cPanel. This can be very helpful if there is any spamming activity and you just want to disable the email service feature for the domain for the time being.

You can run the below commands through SSH console

To suspend email service for a the cPanel user “aacenyor”

whmapi1 suspend_outgoing_email user=aacenyor

For unsuspending the account, please run the below command:

whmapi1 unsuspend_outgoing_email user=aacenyor

If you are not comfortable with SSH, you can also call these through browser XML.

Example:

To suspend
https://hostname.example.com:2087/cpsess##########/xml-api/suspend_outgoing_email?api.version=1&user=aacenyor

where replace hostname.example.com with your hostname
replace cpsess########## with WHM session id.

To un suspend
https://hostname.example.com:2087/cpsess##########/xml-api/unsuspend_outgoing_email?api.version=1&user=aacenyor

For older versions cPanel, you may refer to this below forum from cPanel. There is a workaround

https://forums.cpanel.net/threads/how-do-i-block-one-domain-from-sending-email-from-my-server.223731/#post920912

Installing and managing firewall using ConfigServer Firewall (CSF)

ConfigServer firewall is a popular Linux firewall security suite. It is easy to install, flexible to configure and secure with extra checks.
CSF is generally considered a more advanced firewall as there are more configuration options compared to other firewalls, while still being simple enough to install and configure that even novice administrators can use it. Some of the MANY functions of CSF are given below:-

  • Daemon process that checks for login authentication failures for:
  1. Courier imap, Dovecot, uw-imap, Kerio
  2.  openSSH
  3.  cPanel, WHM, Webmail (cPanel servers only)
  4. Pure-ftpd, vsftpd, Proftpd
  5. Password protected web pages (htpasswd)
  6. Mod_security failures (v1 and v2)
  7. Suhosin failures
  8. Exim SMTP AUTH
  9. Custom login failures with separate log file and regular expression matching

 

  • SSH login notification
  • SU login notification
  • SYN Flood protection
  • Ping of death protection
  • Port Scan tracking and blocking
  • IPv6 Support with ip6tables
  • …lots more!

Removing Your Current Firewall
To prevent any conflicts in operation we will need to remove your current firewall. The most common software firewalls on our dedicated servers are APF and CSF, so we have provided instructions on how to remove APF below. If you are using a different software firewall be sure to follow that programs uninstall directions before continuing. After completing the uninstall continue with the CSF installation below.
Using Yum to Remove APF
If it was installed via yum, which is most likely, you will first need to identify the name of your APF package:
rpm -qa |grep -i apf
In this case:
[root@host ~]# rpm -qa | grep apf
apf-9.6_5-1
In order to remove that package, and get your server ready for CSF installation, run the following command:
[root@host ~]# rpm -e apf-9.6_5-1
If you see this:
[root@host ~ ]# rpm -e apf-9.6_5-1
error: Failed dependencies:
apf >= 9.6_5-1 is needed by (installed) bfd-1.2-1.noarch
It means you have BFD installed, and it will need to be removed before you can proceed to removing APF:
[root@host ~ ]# rpm -e bfd-1.2-1.noarch
Then attempt to remove apf again:
[root@host ~ ]# rpm -e apf-9.6_5-1
Any further dependency errors can be handled in the same way as long as you are aware of what you are removing. If you have any questions or get stuck at any point feel free to contact me here.
Removing Source Installed APF
This can be a bit trickier, and if you are not sure what you’re doing you may want to contact me . If you are confident and wish to proceed you will find a list of commands below that you can use to remove APF if it is installed in the most common CentOS directories.
Stopping APF and iptables clears all of the rules from your firewall and ensures that removing the APF installation won’t cause access problems:
[root@host ~ ]# /etc/init.d/iptables stop

[root@host ~ ]# /etc/init.d/apf stop
Remove all of the APF related files:
[root@host ~ ]# rm -Rfv /etc/apf
[root@host ~ ]# rm -fv /etc/cron.daily/fw
[root@host ~ ]# rm -fv /etc/init.d/apf
Remove APF from the list of programs that start at boot:
[root@host ~ ]# chkconfig apf off

 

Installing CSF

So, login to your server via ssh and let’s start CSF installation by retrieving the package files using wget command:

# wget http://configserver.com/free/csf.tgz

Unpack the archive:

# tar xfvz csf.tgz
Navigate to the uncomperssed csf directory:

# cd csf

 

Check CSF will work on your server
CSF provides a test script. We can check whether CSF works with your Server or not prior to installing it.

#perl csftest.pl 

Testing ip_tables/iptable_filter…OK
Testing ipt_LOG…OK
Testing ipt_multiport/xt_multiport…OK
Testing ipt_REJECT…OK
Testing ipt_state/xt_state…OK
Testing ipt_limit/xt_limit…OK
Testing ipt_recent…OK
Testing xt_connlimit…OK
Testing ipt_owner/xt_owner…OK
Testing iptable_nat/ipt_REDIRECT…OK
Testing iptable_nat/ipt_DNAT…OK

RESULT: csf should function on this server

If you get this output, you can proceed to installation. Otherwise you need to enable each missing modules and then install csf.

Run the installer:
Now there founr installation scripts
install.cpanel.sh For cPanel
install.directadmin.sh
install.generic.sh
install.sh

csf installation for cPanel and DirectAdmin is preconfigured to work on those servers with all the standard ports open.. So install as per your requirement.

#sh install.sh

csf auto-configures your SSH port on installation where it’s running on a non-standard port. CSF also auto-whitelists your connected IP address where possible on installation.
Configuration

By default CSF is in Test mode. So you need to disable the test mode once you configured the firewall correctly. Then only the lfd daemon starts.

“/etc/csf/csf.conf” is the main CSF configuration file.
TCP_IN/TCP_OUT/UDP_IN/UDP_OUT = : These are the ports you want to leave open for your server to operate. If you change the default SSH port make sure to add it here. Also add any other services you might have running such as Shoutcast or game servers. All the ports not mentioed here will be blocked.

LF_DSHIELD = 0: Change this option to 86400. This is an automatic updated list of known attacking IPs. Enabling this will stop them from being able to connect to your server.

Spam Protection Alerts
If you want to add some spam protection, CSF can help. Look in the configuration for the following:

LF_SCRIPT_ALERT = 0 change this to 1. This will send an email alert to the system administrator when the limit configured below is reached within an hour.

LF_SCRIPT_LIMIT = 100 change this to 250. This will alert you when any scripts sends out 250 email messages in an hour.
Providing all the configuration options for CSF here is beyond the scope of the article. Please refer to this README from csf for more details

Note:

If you have installed CSF on cPanel/WHM, it also installs WHM plugin to manage CSF. You can access it from

WHM >> Home >> Plugins >> CnfigServer Firewall
Now TEST all your services to make sure everything is working – SSH, FTP, http. After you do a few quick tests go back into the Firewall Configuration page.

TESTING = 1 change this to 0 and click Change at the bottom. Then Restart csf+lfd using below commands

#csf -r
Or
#/etc/init.d/csf restart

That’s it, the firewall is successfully installed and running!!
Common commands:-

To block an IP Permenently
#csf -d IP

To allow or whitelist IP permenently.
#csf -a IP

To temporary block IP
#csf -td IP

To temporary allow an IP
#csf -ta IP

To check an IP is blocked in firewall
#iptables -nL | grep IP
or
# csf -g IP

To find Reason for block.

#grep IP /var/log/lfd.log

To remove a permanent block
#csf -dr IP

To remove IP from allow list
#csf -ar IP

To disable csf
#csf -x

To enable CSF
#csf -e

To restart
#csf -r
CSF is an increasingly popular alternative to the stock firewalls on some servers. Should you require any other help , please contact me.

 

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