The packet injection process allows an unknown third party to disrupt or intercept packets from the consenting parties that are communicating, which can lead to degradation or blockage of users' ability to utilize certain network services or protocols.
By utilizing raw sockets, NDIS function calls, or direct access to a network adapter kernel mode driver, arbitrary packets can be constructed and injected into a computer network.
Packet injection has been used for: Through the process of running a packet analyzer or packet sniffer on both network service access points trying to establish communication, the results can be compared.
If point A has no record of sending certain packets that show up in the log at point B, and vice versa, then the packet log inconsistencies show that those packets have been forged and injected by an intermediary access point.
Usually TCP resets are sent to both access points to disrupt communication.