These packets often contain unsolicited commercial or network control messages, backscatters, port scans, and worm activities.
The Conficker worm was responsible in 2010[1] for a large amount of background noise generated by viruses looking for new victims.
In addition to malicious activities, misconfigured hardware and leaks from private networks are also sources of background noise.
The newer IPv6 protocol, which has a much larger address space, will make it more difficult for viruses to scan ports and also limit the impact of misconfigured equipment.
[5] Backscatter is a term coined by Vern Paxson to describe Internet background noise resulting from a DDoS attack using multiple spoofed addresses.