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DDoS Deflate

Fork of DDoS Deflate on now inexistent (MediaLayer went out of business) with fixes, improvements and new features.

Original Author: Zaf (Copyright (C) 2005)

Maintainer: Jefferson González

Contributor (BSD support): Marc S. Brooks


(D)DoS Deflate is a lightweight bash shell script designed to assist in the process of blocking a denial of service attack. It utilizes the command below to create a list of IP addresses connected to the server, along with their total number of connections. It is one of the simplest and easiest to install solutions at the software level.

ss -Hntu | awk '{print $6}' | sort | uniq -c | sort -nr

IP addresses with over a pre-configured number of connections are automatically blocked in the server's firewall, which can be direct ipfw, iptables, or Advanced Policy Firewall (APF).

Notable Features

  • IPv6 support.
  • It is possible to whitelist IP addresses, via /etc/ddos/ignore.ip.list.
  • It is possible to whitelist hostnames, via /etc/ddos/
  • IP ranges and CIDR syntax is supported on /etc/ddos/ignore.ip.list
  • Simple configuration file: /etc/ddos/ddos.conf
  • IP addresses are automatically unblocked after a preconfigured time limit (default: 600 seconds)
  • The script can run as a cron job at chosen frequency via the configuration file (default: 1 minute)
  • The script can run as a daemon at chosen frequency via the configuration file (default: 5 seconds)
  • You can receive email alerts when IP addresses are blocked.
  • Control blocking by connection state (see man ss or man nestat).
  • Auto-detection of firewall.
  • Support for APF, CSF, ipfw, and iptables.
  • Logs events to /var/log/ddos.log
  • Can ban only incoming connections or by specific port rules.
  • Option to reduce transfer speed for IP addresses that reach certain limit using iftop and tc.
  • Uses tcpkill to reduce the amount of processes opened by attackers.
  • Cloudflare support by using tcpdump to get the real user ip and using iptables string matching to drop connections.


The installation script has some support to automatically install the required dependencies but, it may fail to install some or all of them. You may want to manually install the required dependencies before proceeding to installation as listed below on the subsection of your linux distro.


sudo apt install dnsutils
sudo apt-get install net-tools
sudo apt-get install tcpdump
sudo apt-get install dsniff -y
sudo apt install grepcidr


As root user execute the following commands:

wget -O
cd ddos-deflate-master


As root user execute the following commands:

cd ddos-deflate-master


The installer will automatically detect if your system supports init.d scripts, systemd services or cron jobs. If one of them is found it will install apropiate files and start the ddos script. In the case of init.d and systemd the ddos script is started as a daemon, which monitoring interval is set at 5 seconds by default. The daemon is much faster detecting attacks than the cron job since cron's are capped at 1 minute intervals.

Once you hava (D)Dos deflate installed proceed to modify the config files to fit your needs.


On this file you can add a list of host names to be whitelisted, for example:


On this file you can add a list of ip addresses to be whitelisted, for example:


The behaviour of the ddos script is modified by this configuration file. For more details see man ddos which has documentation of the different configuration options.

After you modify the config files you will need to restart the daemon. If running on systemd:

systemctl restart ddos

If running as classical init.d script:

/etc/init.d/ddos restart
service ddos restart

When running the script as a cronjob no restarting is required.

CLI Usage

ddos [OPTIONS] [N]

N : number of tcp/udp connections (default 150)


-h | --help:

Show the help screen.

-c | --cron:

Create cron job to run the script regularly (default 1 mins).

-i | --ignore-list:

List whitelisted ip addresses.

-b | --bans-list:

List currently banned ip addresses.

-u | --unban:

Unbans a given ip address.

-d | --start:

Initialize a daemon to monitor connections.

-s | --stop:

Stop the daemon.

-t | --status:

Show status of daemon and pid if currently running.

-v[4|6] | --view [4|6]:

Display active connections to the server.

-y[4|6] | --view-port [4|6]:

Display active connections to the server including the port.

-k | --kill:

Block all ip addresses making more than N connections.