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Note

Applies to VoipNow 3.X.X and upper versions!

An increased number of VoIP attacks (mostly brute-force) coming from specific countries usually leads to excessive resource utilization and eventually to fraud calls, if the attack is successful. If successful, such attacks might eventually lead to fraud calls. One way to avoid this situation is by blocking specific countries (- one or several)more.

Step-by-step guide

...

Before starting

It is assumed that you are using a CentOS 7 server with already having iptables already and ipset installed. Run the following command in order to double check the availability of the packages:

Shell

yum list ipset iptables ipset-service iptables-services

In case all are listed under "Installed Packages" section, you can proceed forward. Otherwise, just install the missing packages.

Shell

yum install ipset iptables ipset iptables ipset-service iptables-services

Step-by-step guide

  1. Download the script.

    Shell

     wget wget -O blockcountry.pl  https://raw.githubusercontent.com/4psa/voipnowtoolbox/master/blockcountry.pl

  2. Install the LWP::UserAgent library required perl libraries using the following command. As one of them is available only on EPEL, the EPEL Repository must be added first:

    Shell

    yum install epel-release perl-libwww-perl perl-Locale-SubCountry

  3. Edit the blockcountry.pl script and specify

    the

    which countries

    that

    you want to block.

     The

    The list of countries is

    available 

    available here.

     
    e.g. The code for Palestina is PS. For Turkey, it's TR.
    Run the blockcountry.pl script: 

    Code Block
    languageperl
    my @countries = (
            "PS",
            "SA",
            "TR",
            );
    
    
  4. Run the blockcountry.pl script:

    Shell

    perl blockcountry.pl

    The default policy is set to reject. The iptables rules for the above example look like this:

    Code Block
    Chain INPUT (policy ACCEPT)
    target     prot opt source               destination
    REJECT     all  --  0.0.0.0/0            0.0.0.0/0            match-set Turkey src reject-with icmp-host-unreachable
    REJECT     all  --  0.0.0.0/0            0.0.0.0/0            match-set Saudi_Arabia src reject-with icmp-host-unreachable
    REJECT     all  --  0.0.0.0/0            0.0.0.0/0            match-set Palestinian_Territory_Occupied src reject-with icmp-host-unreachable
    
    

    If you want to add the iptables rules with ACCEPT or DROP instead of reject, you can call the script with -p parameter.

    Shell

    perl blockcountry.pl -p drop

    It will add the iptables rule as follows:

    Code Block
    Chain INPUT (policy ACCEPT)
    target     prot opt source               destination
    DROP	   all  --  0.0.0.0/0            0.0.0.0/0            match-set Turkey src
    DROP	   all  --  0.0.0.0/0            0.0.0.0/0            match-set Saudi_Arabia src
    DROP	   all  --  0.0.0.0/0            0.0.0.0/0            match-set Palestinian_Territory_Occupied src
    
    

    Daily refresh of the IP sets can be done via a cronjob like the one below:

    Code Block
    * 1 * * * /usr/bin/perl /<path_to_the_script>/blockcountry.pl -r > /dev/null 2>&1

    Replace <path_to_the_script> with the actual path toward the blockcountry.pl script.

    If you need to flush the existing rules and destroy all the IP sets available, use the parameter -f like this:

    Shell

    perl blockcountry.pl -f

    Just answer Yes or Y and all the rules and sets will be removed.

  5. To preserve the rules during reboots, run the following comandcommand: 

    Shell

    service iptables save && chkconfig iptables onservice ipset save

Note

Make sure you do not mix up the countries, otherwise you might get yourself blocked.

To avoid such issues, it is recommended to start with a cronjob that will remove the rules in order to avoid issues. If no issues arise, the cronjob can be removed.

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