Information about WiFi

The Wi-Fi logo used by the Wi-Fi Alliance .
Wi-Fi , also spelled Wifi or WiFi , is a popular technology
that allows an electronic device to exchange data or
connect to the internet wirelessly using radio waves.
The name is a trademark name, and was stated to be a
play on the audiophile term Hi-Fi . The Wi-Fi Alliance
defines Wi-Fi as any " wireless local area network (WLAN)
products that are based on the Institute of Electrical and
Electronics Engineers ' (IEEE) 802.11 standards". [1]
However, since most modern WLANs are based on these
standards, the term "Wi-Fi" is used in general English as
a synonym for "WLAN". Only Wi-Fi products that
complete Wi-Fi Alliance interoperability certification
testing successfully may use the "Wi-Fi CERTIFIED"
trademark.
Many devices can use Wi-Fi, e.g., personal computers,
video-game consoles, smartphones , some digital
cameras, tablet computers and digital audio players.
These can connect to a network resource such as the
Internet via a wireless network access point. Such an
access point (or hotspot) has a range of about 20 meters
(65 feet) indoors and a greater range outdoors. Hotspot
coverage can comprise an area as small as a single room
with walls that block radio waves, or as large as many
square miles achieved by using multiple overlapping
access points.
Depiction of a device sending information wirelessly to
another device, both connected to the local network, in
order to print a document.
Wi-Fi can be less secure than wired connections (such
as Ethernet) because an intruder does not need a
physical connection. Web pages that use SSL are secure
but unencrypted internet access can easily be detected
by intruders. Because of this, Wi-Fi has adopted various
encryption technologies. The early encryption WEP ,
proved easy to break. Higher quality protocols ( WPA,
WPA2) were added later. An optional feature added in
2007, called Wi-Fi Protected Setup (WPS), had a serious
flaw that allowed an attacker to recover the router's
password. [2] The Wi-Fi Alliance has since updated its
test plan and certification program to ensure all newly
certified devices resist attacks.
History
Main article: History of IEEE 802.11
802.11 technology has its origins in a 1985 ruling by the
US Federal Communications Commission that released
the ISM band for unlicensed use. [3] In 1991, NCR
Corporation with AT&T Corporation invented the
precursor to 802.11 intended for use in cashier systems.
The first wireless products were under the name
WaveLAN .
The 802.11 standard uses a large number of patents held
by many different organizations. [4]
Some have dubbed Dutch engineer Vic Hayes the "father
of Wi-Fi" due to his involvement in negotiating the
initial standards within the IEEE while chairing the
workgroup.[5][6]
The Australian radio-astronomer John O'Sullivan
developed a key patent used in Wi-Fi as a by-product in
a CSIRO research project, "a failed experiment to detect
exploding mini black holes the size of an atomic
particle". [7] In 1992 and 1996, Australian organization
CSIRO (the Australian Commonwealth Scientific and
Industrial Research Organisation
) obtained patents [8] for a method later used in Wi-Fi to
"unsmear" the signal.[9]
In 1999, the Wi-Fi Alliance formed as a trade association
to hold the Wi-Fi trademark under which most products
are sold. [10]
In April 2009, 14 technology companies agreed to pay
CSIRO $250 million for infringements on CSIRO patents.
[11] This led to Australians labelling Wi-Fi as an
Australian invention, [12] though this has been the
subject of some controversy. [13][14] CSIRO won a further
$220 million settlement for Wi-Fi patent-infringements in
2012 with global firms in the United States required to
pay the CSIRO licensing rights estimated to be worth an
additional $1 billion in royalties. [11][15][16]
The name
The term Wi-Fi , commercially used at least as early as
August 2000, [17] was coined by a brand-consulting firm
called Interbrand Corporation. The Wi-Fi Alliance had
hired Interbrand to determine a name that was "a little
catchier than 'IEEE 802.11b Direct Sequence'". [18][19][20]
Phil Belanger, a founding member of the Wi-Fi Alliance
who presided over the selection of the name "Wi-Fi",
also stated that Interbrand invented Wi-Fi as a play on
words with Hi-Fi (high fidelity), and also created the Wi-
Fi logo. The term ' fidelity ' refers to the faithfulness/
accuracy of reproduction or transmission of the signal,
and ' wireless' is a distinguishing feature that contrasted
with earlier internet connection technologies such as
wired Ethernet.
The Wi-Fi Alliance initially used the advertising slogan
"The Standard for Wireless Fidelity", [18] for Wi-Fi but
later removed the phrase from their marketing. Despite
this, some documents from the Alliance dated 2003 and
2004 still contain the term Wireless Fidelity.[21][22] There
was no official statement related to the dropping of the
term.
The yin-yang Wi-Fi logo indicates the certification of a
product for interoperability .[21]
Non-Wi-Fi technologies intended for fixed points such
as Motorola Canopy are usually described as fixed
wireless. Alternative wireless technologies include
mobile phone standards such as 2G, 3G or 4G .
Wi-Fi certification
See also: Wi-Fi Alliance
The IEEE does not test equipment for compliance with
their standards. The non-profit Wi-Fi Alliance was
formed in 1999 to fill this void — to establish and
enforce standards for interoperability and backward
compatibility , and to promote wireless local-area-
network technology. As of 2010, the Wi-Fi Alliance
consisted of more than 375 companies from around the
world.[23][24] The Wi-Fi Alliance enforces the use of the
Wi-Fi brand to technologies based on the IEEE 802.11
standards from the IEEE. This includes wireless local
area network (WLAN) connections, device to device
connectivity (such as Wi-Fi Peer to Peer aka Wi-Fi
Direct), Personal area network (PAN), local area network
(LAN) and even some limited wide area network (WAN)
connections. Manufacturers with membership in the Wi-
Fi Alliance, whose products pass the certification
process, gain the right to mark those products with the
Wi-Fi logo.
Specifically, the certification process requires
conformance to the IEEE 802.11 radio standards, the WPA
and WPA2 security standards, and the EAP
authentication standard. Certification may optionally
include tests of IEEE 802.11 draft standards, interaction
with cellular-phone technology in converged devices,
and features relating to security set-up, multimedia, and
power-saving. [25]
Not every Wi-Fi device is submitted for certification. The
lack of Wi-Fi certification does not necessarily imply
that a device is incompatible with other Wi-Fi devices. If
it is compliant or partly compatible, the Wi-Fi Alliance
may not object to its description as a Wi-Fi device
[citation needed] though technically only certified
devices are approved. The Wi-Fi Alliance may or may not
sanction derivative terms, such as Super Wi-Fi , coined
by the US Federal Communications Commission (FCC) to
describe proposed networking in the UHF TV band in the
US.
Uses
A sticker indicating to the public that a location is
within range of a Wi-Fi network. A dot with curved lines
radiating from it is a common symbol for Wi-Fi,
representing a point transmitting a signal.[26]
To connect to a Wi-Fi LAN, a computer has to be
equipped with a wireless network interface controller .
The combination of computer and interface controller is
called a station . All stations share a single radio
frequency communication channel. Transmissions on
this channel are received by all stations within range.
The hardware does not signal the user that the
transmission was delivered and is therefore called a
best-effort delivery mechanism. A carrier wave is used
to transmit the data in packets, referred to as "Ethernet
frames". Each station is constantly tuned in on the radio
frequency communication channel to pick up available
transmissions.
Internet access
A Wi-Fi-enabled device can connect to the Internet
when within range of a wireless network which is
configured to permit this. The coverage of one or more
(interconnected) access points —called hotspots—can
extend from an area as small as a few rooms to as large
as many square miles. Coverage in the larger area may
require a group of access points with overlapping
coverage. Outdoor public Wi-Fi technology has been
used successfully in wireless mesh networks in London,
UK.
Wi-Fi provides service in private homes, high street
chains and independent businesses, as well as in public
spaces at Wi-Fi hotspots set up either free-of-charge or
commercially, often using a Captive portal webpage for
access. Organizations and businesses , such as airports,
hotels, and restaurants, often provide free-use hotspots
to attract customers. Enthusiasts or authorities who
wish to provide services or even to promote business in
selected areas sometimes provide free Wi-Fi access.
Routers that incorporate a digital subscriber line modem
or a cable modem and a Wi-Fi access point, often set up
in homes and other buildings, provide Internet access
and internetworking to all devices connected to them,
wirelessly or via cable.
Similarly, there are battery-powered routers that include
a cellular mobile Internet radiomodem and Wi-Fi access
point. When subscribed to a cellular phone carrier, they
allow nearby Wi-Fi stations to access the Internet over
2G, 3G, or 4G networks. Many smartphones have a built-
in capability of this sort, including those based on
Android, BlackBerry, Bada, iOS ( iPhone), Windows Phone
and Symbian, though carriers often disable the feature,
or charge a separate fee to enable it, especially for
customers with unlimited data plans. "Internet packs"
provide standalone facilities of this type as well, without
use of a smartphone; examples include the MiFi - and
WiBro -branded devices. Some laptops that have a
cellular modem card can also act as mobile Internet Wi-
Fi access points.
Wi-Fi also connects places that normally don't have
network access, such as kitchens and garden sheds.
City-wide Wi-Fi
Further information: Municipal wireless network
An outdoor Wi-Fi access point
In the early 2000s, many cities around the world
announced plans to construct city-wide Wi-Fi networks.
There are many successful examples; in 2004, Mysore
became India's first Wi-Fi-enabled city and second in
the world after Jerusalem. A company called WiFiyNet
has set up hotspots in Mysore, covering the complete
city and a few nearby villages. [27]
In 2005, Sunnyvale, California, became the first city in
the United States to offer city-wide free Wi-Fi. [28]
Minneapolis has generated $1.2 million in profit annually
for its provider.[29]
In May 2010, London , UK, Mayor Boris Johnson pledged
to have London-wide Wi-Fi by 2012. [30] Several
boroughs including Westminster and Islington [31][32]
already have extensive outdoor Wi-Fi coverage.
Officials in South Korea's capital are moving to provide
free Internet access at more than 10,000 locations
around the city, including outdoor public spaces, major
streets and densely populated residential areas. Seoul
will grant leases to KT, LG Telecom and SK Telecom.
The companies will invest $44 million in the project,
which will be completed in 2015.[33]
Campus-wide Wi-Fi
Many traditional college campuses in the United States
provide at least partial wireless Wi-Fi Internet coverage.
Carnegie Mellon University built the first campus-wide
wireless Internet network, called Wireless Andrew , at its
Pittsburgh campus in 1993 before Wi-Fi branding
originated. [34][35][36] In Europe many universities
collaborate in providing Wi-Fi access to students and
staff through the eduroam international authentication
infrastructure.
In 2000, Drexel University in Philadelphia became the
United States' first major university to offer completely
wireless Internet access across its entire campus.[37]
The Far Eastern University in Manila is the first university
in the Philippines to implement a campus-wide Wi-Fi
coverage.
Direct computer-to-computer communications
Wi-Fi also allows communications directly from one
computer to another without an access point
intermediary. This is called ad hoc Wi-Fi transmission.
This wireless ad hoc network mode has proven popular
with multiplayer handheld game consoles , such as the
Nintendo DS , PlayStation Portable , digital cameras, and
other consumer electronics devices. Some devices can
also share their Internet connection using ad hoc,
becoming hotspots or "virtual routers". [38]
Similarly, the Wi-Fi Alliance promotes a specification
called Wi-Fi Direct for file transfers and media sharing
through a new discovery- and security-methodology. [39]
Wi-Fi Direct launched in October 2010. [40]
Advantages and limitations
A keychain-size Wi-Fi detector
Advantages
Wi-Fi allows cheaper deployment of local area networks
(LANs). Also spaces where cables cannot be run, such
as outdoor areas and historical buildings, can host
wireless LANs.
Manufacturers are building wireless network adapters
into most laptops. The price of chipsets for Wi-Fi
continues to drop, making it an economical networking
option included in even more devices. [citation needed]
Different competitive brands of access points and client
network-interfaces can inter-operate at a basic level of
service. Products designated as "Wi-Fi Certified" by the
Wi-Fi Alliance are backwards compatible. Unlike mobile
phones, any standard Wi-Fi device will work anywhere
in the world.
Wi-Fi Protected Access encryption (WPA2) is considered
secure, provided a strong passphrase is used. New
protocols for quality-of-service ( WMM ) make Wi-Fi more
suitable for latency-sensitive applications (such as
voice and video). Power saving mechanisms (WMM
Power Save) extend battery life.
Limitations
Spectrum assignments and operational limitations are
not consistent worldwide: Australia and Europe allow for
an additional two channels beyond those permitted in
the US for the 2.4 GHz band (1–13 vs. 1–11), while
Japan has one more on top of that (1–14).
A Wi-Fi signal occupies five channels in the 2.4 GHz
band. Any two channel numbers that differ by five or
more, such as 2 and 7, do not overlap. The oft-repeated
adage that channels 1, 6, and 11 are the only non-
overlapping channels is, therefore, not accurate.
Channels 1, 6, and 11 are the only group of three non-
overlapping channels in North America and the United
Kingdom. In Europe and Japan using Channels 1, 5, 9,
and 13 for 802.11g and 802.11n is recommended.[ citation
needed]
Equivalent isotropically radiated power (EIRP) in the EU
is limited to 20 dBm (100 mW).
The current 'fastest' norm, 802.11n, uses double the
radio spectrum/bandwidth (40 MHz) compared to
802.11a or 802.11g (20 MHz). [citation needed ] This
means there can be only one 802.11n network on the 2.4
GHz band at a given location, without interference to/
from other WLAN traffic. 802.11n can also be set to use
20 MHz bandwidth only to prevent interference in dense
community.[citation needed]
Range
See also: Long-range Wi-Fi
Wi-Fi networks have limited range. A typical wireless
access point using 802.11b or 802.11g with a stock
antenna might have a range of 35 m (120 ft) indoors and
100 m (300 ft) outdoors. IEEE 802.11n , however, can more
than double the range.[41] Range also varies with
frequency band. Wi-Fi in the 2.4 GHz frequency block
has slightly better range than Wi-Fi in the 5 GHz
frequency block which is used by 802.11a and optionally
by 802.11n. On wireless routers with detachable
antennas, it is possible to improve range by fitting
upgraded antennas which have higher gain in particular
directions. Outdoor ranges can be improved to many
kilometers through the use of high gain directional
antennas at the router and remote device(s). In general,
the maximum amount of power that a Wi-Fi device can
transmit is limited by local regulations, such as FCC Part
15 in the US.
Due to reach requirements for wireless LAN applications,
Wi-Fi has fairly high power consumption compared to
some other standards. Technologies such as Bluetooth
(designed to support wireless PAN applications) provide
a much shorter propagation range between 1 and 100m
[42] and so in general have a lower power consumption.
Other low-power technologies such as ZigBee have fairly
long range, but much lower data rate. The high power
consumption of Wi-Fi makes battery life in mobile
devices a concern.
Researchers have developed a number of "no new wires"
technologies to provide alternatives to Wi-Fi for
applications in which Wi-Fi's indoor range is not
adequate and where installing new wires (such as
CAT-6 ) is not possible or cost-effective. For example,
the ITU-T G.hn standard for high speed Local area
networks uses existing home wiring (coaxial cables ,
phone lines and power lines ). Although G.hn does not
provide some of the advantages of Wi-Fi (such as
mobility or outdoor use), it's designed for applications
(such as IPTV distribution) where indoor range is more
important than mobility.
Due to the complex nature of radio propagation at
typical Wi-Fi frequencies, particularly the effects of
signal reflection off trees and buildings, algorithms can
only approximately predict Wi-Fi signal strength for any
given area in relation to a transmitter. [43] This effect
does not apply equally to long-range Wi-Fi , since longer
links typically operate from towers that transmit above
the surrounding foliage.
The practical range of Wi-Fi essentially confines mobile
use to such applications as inventory-taking machines
in warehouses or in retail spaces, barcode -reading
devices at check-out stands, or receiving/shipping
stations. Mobile use of Wi-Fi over wider ranges is
limited, for instance, to uses such as in an automobile
moving from one hotspot to another. Other wireless
technologies are more suitable for communicating with
moving vehicles.
Data security risks
The most common wireless encryption -standard, Wired
Equivalent Privacy (WEP), has been shown to be easily
breakable even when correctly configured. Wi-Fi
Protected Access (WPA and WPA2) encryption, which
became available in devices in 2003, aimed to solve this
problem. Wi-Fi access points typically default to an
encryption-free ( open) mode. Novice users benefit from
a zero-configuration device that works out-of-the-box,
but this default does not enable any wireless security,
providing open wireless access to a LAN. To turn
security on requires the user to configure the device,
usually via a software graphical user interface (GUI). On
unencrypted Wi-Fi networks connecting devices can
monitor and record data (including personal information)
. Such networks can only be secured by using other
means of protection, such as a VPN or secure Hypertext
Transfer Protocol (HTTPS ) over Transport Layer Security .
Interference
For more details on this topic, see Electromagnetic
interference at 2.4 GHz.
Wi-Fi connections can be disrupted or the internet
speed lowered by having other devices in the same area.
Many 2.4 GHz 802.11b and 802.11g access-points default
to the same channel on initial startup, contributing to
congestion on certain channels. Wi-Fi pollution, or an
excessive number of access points in the area,
especially on the neighboring channel, can prevent
access and interfere with other devices' use of other
access points, caused by overlapping channels in the
802.11g/b spectrum, as well as with decreased signal-
to-noise ratio (SNR) between access points. This can
become a problem in high-density areas, such as large
apartment complexes or office buildings with many Wi-Fi
access points.
Additionally, other devices use the 2.4 GHz band:
microwave ovens, ISM band devices, security cameras,
ZigBee devices, Bluetooth devices, video senders ,
cordless phones, baby monitors, and (in some
countries) Amateur radio all of which can cause
significant additional interference. It is also an issue
when municipalities [44] or other large entities (such as
universities) seek to provide large area coverage.
Hardware
Standard devices
An embedded RouterBoard 112 with U.FL - RSMA pigtail
and R52 mini PCI Wi-Fi card widely used by wireless
Internet service providers (WISPs ) in the Czech Republic
OSBRiDGE 3GN – 802.11n Access Point and UMTS/GSM
Gateway in one device
An Atheros Wi-Fi N draft adaptor with built in Bluetooth
on a Sony Vaio E series laptop
USB wireless adapter
A wireless access point (WAP) connects a group of
wireless devices to an adjacent wired LAN . An access
point resembles a network hub , relaying data between
connected wireless devices in addition to a (usually)
single connected wired device, most often an Ethernet
hub or switch, allowing wireless devices to
communicate with other wired devices.
Wireless adapters allow devices to connect to a wireless
network. These adapters connect to devices using
various external or internal interconnects such as PCI,
miniPCI, USB , ExpressCard , Cardbus and PC Card. As of
2010, most newer laptop computers come equipped with
built in internal adapters.
Wireless routers integrate a Wireless Access Point,
Ethernet switch, and internal router firmware application
that provides IP routing , NAT , and DNS forwarding
through an integrated WAN -interface. A wireless router
allows wired and wireless Ethernet LAN devices to
connect to a (usually) single WAN device such as a
cable modem or a DSL modem. A wireless router allows
all three devices, mainly the access point and router, to
be configured through one central utility. This utility is
usually an integrated web server that is accessible to
wired and wireless LAN clients and often optionally to
WAN clients. This utility may also be an application that
is run on a computer, as is the case with as Apple's
AirPort , which is managed with the AirPort Utility on
Mac OS X and iOS.[45]
Wireless network bridges connect a wired network to a
wireless network. A bridge differs from an access point:
an access point connects wireless devices to a wired
network at the data-link layer . Two wireless bridges may
be used to connect two wired networks over a wireless
link, useful in situations where a wired connection may
be unavailable, such as between two separate homes.
Wireless range-extenders or wireless repeaters can
extend the range of an existing wireless network.
Strategically placed range-extenders can elongate a
signal area or allow for the signal area to reach around
barriers such as those pertaining in L-shaped corridors.
Wireless devices connected through repeaters will suffer
from an increased latency for each hop, as well as from a
reduction in the maximum data throughput that is
available. In addition, the effect of additional users using
a network employing wireless range-extenders is to
consume the available bandwidth faster than would be
the case where but a single user migrates around a
network employing extenders. For this reason, wireless
range-extenders work best in networks supporting very
low traffic throughput requirements, such as for cases
where but a single user with a Wi-Fi equipped tablet
migrates around the combined extended and non-
extended portions of the total connected network.
Additionally, a wireless device connected to any of the
repeaters in the chain will have a data throughput that is
also limited by the "weakest link" existing in the chain
between where the connection originates and where the
connection ends. Networks employing wireless
extenders are also more prone to degradation from
interference from neighboring access points that border
portions of the extended network and that happen to
occupy the same channel as the extended network.
The security standard, Wi-Fi Protected Setup , allows
embedded devices with limited graphical user interface
to connect to the Internet with ease. Wi-Fi Protected
Setup has 2 configurations: The Push Button
configuration and the PIN configuration. These
embedded devices are also called The Internet of Things
and are low-power, battery-operated embedded
systems. A number of Wi-Fi manufacturers design chips
and modules for embedded Wi-Fi, such as GainSpan.[46]
Distance records
Distance records (using non-standard devices) include
382 km (237 mi) in June 2007, held by Ermanno
Pietrosemoli and EsLaRed of Venezuela, transferring
about 3 MB of data between the mountain-tops of El
Águila and Platillon.[47][48] The Swedish Space Agency
transferred data 420 km (260 mi), using 6 watt amplifiers
to reach an overhead stratospheric balloon. [49]
Embedded systems
Embedded serial-to-Wi-Fi module
Increasingly in the last few years (particularly as of
2007), embedded Wi-Fi modules have become available
that incorporate a real-time operating system and
provide a simple means of wirelessly enabling any
device which has and communicates via a serial port.
[50] This allows the design of simple monitoring
devices. An example is a portable ECG device monitoring
a patient at home. This Wi-Fi-enabled device can
communicate via the Internet.[51]
These Wi-Fi modules are designed by OEMs so that
implementers need only minimal Wi-Fi knowledge to
provide Wi-Fi connectivity for their products.
Multiple access points
Increasing the number of Wi-Fi access points provides
network redundancy, support for fast roaming and
increased overall network-capacity by using more
channels or by defining smaller cells . Except for the
smallest implementations (such as home or small office
networks), Wi-Fi implementations have moved toward
"thin" access points, with more of the network
intelligence housed in a centralized network appliance,
relegating individual access points to the role of "dumb"
transceivers. Outdoor applications may use mesh
topologies.
Network security
Main article: Wireless security
The main issue with wireless network security is its
simplified access to the network compared to traditional
wired networks such as Ethernet, with wired networking
one must either gain access to a building (physically
connecting into the internal network) or break through
an external firewall . To enable Wi-Fi, one merely needs
to be within the wireless range of the Wi-Fi network.
Most business networks protect sensitive data and
systems by attempting to disallow external access.
Enabling wireless connectivity reduces security if the
network uses inadequate or no encryption. [52][53]
An attacker who has gained access to a Wi-Fi network
router can initiate a DNS spoofing attack against any
other user of the network by forging a response before
the queried DNS server has a chance to reply.[54]
Securing methods
A common measure to deter unauthorized users involves
hiding the access point's name by disabling the SSID
broadcast. While effective against the casual user, it is
ineffective as a security method because the SSID is
broadcast in the clear in response to a client SSID query.
Another method is to only allow computers with known
MAC addresses to join the network, [55] but determined
eavesdroppers may be able to join the network by
spoofing an authorized address.
Wired Equivalent Privacy (WEP) encryption was designed
to protect against casual snooping but it is no longer
considered secure. Tools such as AirSnort or Aircrack-
ng can quickly recover WEP encryption keys.[56]
Because of WEP's weakness the Wi-Fi Alliance approved
Wi-Fi Protected Access (WPA) which uses TKIP . WPA
was specifically designed to work with older equipment
usually through a firmware upgrade. Though more secure
than WEP, WPA has known vulnerabilities.
The more secure WPA2 using Advanced Encryption
Standard was introduced in 2004 and is supported by
most new Wi-Fi devices. WPA2 is fully compatible with
WPA.[57]
A flaw in a feature added to Wi-Fi in 2007, called Wi-Fi
Protected Setup, allows WPA and WPA2 security to be
bypassed and effectively broken in many situations. The
only remedy as of late 2011 is to turn off Wi-Fi Protected
Setup, [58] which is not always possible.
Piggybacking
Main article: Piggybacking (Internet access)
Further information: Legality of piggybacking
Piggybacking refers to access to a wireless Internet
connection by bringing one's own computer within the
range of another's wireless connection, and using that
service without the subscriber's explicit permission or
knowledge.
During the early popular adoption of 802.11 , providing
open access points for anyone within range to use was
encouraged[by whom? ] to cultivate wireless community
networks , [59] particularly since people on average use
only a fraction of their downstream bandwidth at any
given time.
Recreational logging and mapping of other people's
access points has become known as wardriving. Indeed,
many access points are intentionally installed without
security turned on so that they can be used as a free
service. Providing access to one's Internet connection in
this fashion may breach the Terms of Service or contract
with the ISP. These activities do not result in sanctions
in most jurisdictions; however, legislation and case law
differ considerably across the world. A proposal to leave
graffiti describing available services was called
warchalking .[60] A Florida court case determined that
owner laziness was not to be a valid excuse. [citation
needed]
Piggybacking often occurs unintentionally, since most
access points are configured without encryption by
default[ citation needed] and operating systems can be
configured to connect automatically to any available
wireless network. A user who happens to start up a
laptop in the vicinity of an access point may find the
computer has joined the network without any visible
indication. Moreover, a user intending to join one
network may instead end up on another one if the latter
has a stronger signal. In combination with automatic
discovery of other network resources (see DHCP and
Zeroconf ) this could possibly lead wireless users to
send sensitive data to the wrong middle-man when
seeking a destination ( see Man-in-the-middle attack ).
For example, a user could inadvertently use an unsecure
network to log into a website, thereby making the login
credentials available to anyone listening, if the website
uses an unsecure protocol such as HTTP .
Safety
Further information: Wireless electronic devices and
health
The World Health Organization (WHO) says "there is no
risk from low level, long-term exposure to wi-fi
networks" and the United Kingdom's Health Protection
Agency reports that exposure to Wi-Fi for a year results
in the "same amount of radiation from a 20-minute
mobile phone call". [61][62]
A small percentage of Wi-Fi users have reported adverse
health issues after repeat exposure and use of Wi-Fi, [63]
though there has been no publication of any effects
being observable in double-blind studies . A review of
studies involving 725 people that claimed
electromagnetic hypersensitivity found no evidence for
their claims. [64]