1. IPTables
Getting Started
Nishanth Kumar
n|u Bangalore chapter member
n|u / OWASP / G4H / SecurityXploded meet
22 Feb 2014

2. Agenda
• Firewall Basics
• Packet Basics
• Linux Firewalls
• What you can do with IPTables
• What you can’t do with IP Tables
• What you need to know about IP Tables
• Few Examples & Demo
22 Feb 2014

3. Firewalls
 Prevents Unauthorized access TO or FROM network.
 Hardware / Software / both
22 Feb 2014

4. What Firewalls do ?
 Filtering traffic based on POLICY
 Policy determines what is acceptable traffic
 Access control over traffic
 Accept or Deny
 May perform other duties
 Logging ( Forensics , SLA )
 Flagging ( Intrusion Detection )
 QOS ( bandwidth management , inbound &outbound traffic
priority )
22 Feb 2014

5. Typical Packet looks like …
22 Feb 2014

6. Linux Firewalls
 IP Cop
 Shore wall
 UFW – Uncomplicated Firewall
 Open BSD & PF
Most of the above firewall intern uses IPTables .
22 Feb 2014

7. Some basic commands
 service iptables status
 The above command is used to check the status of iptables
 service iptables start
 The above command is used to start the iptables
 service iptables stop
 The above command is used to stop the iptables
 iptables –F or iptables --flush
 The above command is used to clean-up all the default rules
and existing rules.
22 Feb 2014

8. Ping Block - DROP
iptables -A INPUT -p icmp -j DROP
22 Feb 2014

9. Description of rule
iptables -A INPUT -p icmp -j DROP
Service
PROTOCOL
NAME
APPEND
INPUT Chain
JUMP
PROTOCOL
TARGET
22 Feb 2014

10. Ping Block - REJECT
iptables -A INPUT -p icmp -j REJECT
22 Feb 2014

11. Description of rule
iptables -A INPUT -p icmp -j REJECT
Service
PROTOCOL
NAME
APPEND
INPUT Chain
JUMP
PROTOCOL
TARGET
22 Feb 2014

12. Web Server - Client Example
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP
22 Feb 2014

13. Description of rule
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP
Service
APPEND
INPUT
INTERFACE
INPUT Chain
PROTOCOL
NAME
Port
Number
PROTOCOL
JUMP
INTERFACE NAME
Destination Port
TARGET
22 Feb 2014

14. Web Server - Client Example - 1
192.168.99.12
192.168.99.11
iptables -A INPUT –s 192.168.99.12 -p tcp --dport 80 -j DROP
22 Feb 2014

15. Description of rule
iptables -A INPUT -s 192.168.99.12 -p tcp --dport 80 -j DROP
Service
APPEND
Source
PROTOCOL
NAME
Port
Number
INPUT Chain
PROTOCOL
JUMP
IP Address of the Source
Destination Port
TARGET
22 Feb 2014

16. Continue in Part 2
Thank you
22 Feb 2014