In computer networking, a mangled or invalid packet is a packet — especially IP

Internet protocol suite

The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...

 packet — that either lacks order or self-coherence, or contains code aimed to confuse or disrupt computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s, firewalls, routers, or any service present on the network.

Mangled packets can be generated by dedicated software such as nmap

Nmap

Nmap is a security scanner originally written by Gordon Lyon used to discover hosts and services on a computer network, thus creating a "map" ofthe network...

 or Nessus

Nessus (software)

In computer security, Nessus is a proprietary comprehensive vulnerability scanning program. It is free of charge for personal use in a non-enterprise environment. Its goal is to detect potential vulnerabilities on the tested systems. For example:...

. Their usage is associated with a type of network attack called a denial-of-service (DoS) attack. It aims to destabilize the network and sometimes to reveal its available services – when network operators must restart the disabled ones.

, most invalid packets are easily filtered by modern stateful firewall

Stateful firewall

In computing, a stateful firewall is a firewall that keeps track of the state of network connections traveling across it. The firewall is programmed to distinguish legitimate packets for different types of connections...

s.