What is IP address spoofing?

In Computer Networking, IP address spoofing or IP spoofing is the creation of IP packets with a forged source IP address. This is often done for the purpose of concealing the identity of the sender or impersonating another computing system.

How is IP spoofing done?

Each IP packet contains a source IP address and a destination IP address in its header. By forging the header, one can change the source IP address so that the packet will appear to come from a different IP address. The machine that gets the spoofed IP packets will send a response to the forged source address. Usually, attackers do not care about the response of the IP packets, or they guess the response. You can get more information here: How does IP spoofing work?

Why is IP spoofing done?

IP spoofing is done by attackers mainly for denial-of-service (DoS) attacks. The attackers send an overwhelming number of IP packets to a machine forging the source IP addresses and do not care about the responses of the sent packets. They normally select different IP addresses as source addresses, and as a result, it becomes difficult for the target system to filter out those packets. As a result, the target machine becomes overburdened with network traffic.

IP spoofing is also done by network intruders to defeat network security measures. Sometimes, machines internal to a network trust each other without authentication. So, an attacker often spoofs the IP of a trusted machine and accesses the target machine without authentication.

How to prevent IP spoofing?

Packet filtering is one way of defending against IP spoofing attacks. The gateway should block all the packets that come from outside the network but have a source address that is internal to the network.

Sometimes, upper-layer protocols provide their own way of defending against IP spoofing attacks. For example, at the time of establishing a TCP connection, sometimes random numbers are exchanged between the two machines that establish a connection. If the attacker does not receive the response, it won’t be possible for him to successfully establish a TCP connection. However, due to poor implementation on older Operating Systems or network devices, sometimes attackers can guess the sequence numbers.

The above article gave a brief overview of IP address spoofing. Interested readers can get more information here:

• What is the Smurf attack?
• What is ARP spoofing?
• What are Ping Flood and Ping of Death attacks?
• What is a Fast Flux Network?

I hope this helps. Interested readers who want to know more about how different malware and cyberattacks work and how we can prevent them may want to refer to the book “A Guide To Cyber Security.”

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