From Wikipedia: https://en.wikipedia.org/wiki/Internet_background_noise
Internet background noise (IBN, also known as Internet background radiation) consists of data packets on the Internet which are addressed to IP addresses or ports where there is no network device set up to receive them. These packets often contain unsolicited commercial or network control messages, or are the result of port scans and worm activities. The Conficker worm in particular is responsible 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. For example, some DSL modems have a hard-coded IP address to look up the correct time.
As of November 2010, it is estimated that 5.5 gigabits of background noise is generated every second. It is also thought that a modem user loses about 20 bits per second of their bandwidth to unsolicited traffic. Over the past decade, the amount of background noise for a section of the IPv4 address block that contains 17 million address, has increased from 1 to 50 Mbit/s. 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.
Internet background noise has been used to detect significant changes in Internet traffic and connectivity during the 2011 political unrest from IP address blocks that were geolocated to Libya.