During the early popular adoption of 802.11, providing open access points for anyone within range to use was encouraged to cultivate wireless community networks;particularly since people on average use only a fraction of their upstream bandwidth at any given time. Later, equipment manufacturers and mass-media advocated isolating users to a predetermined whitelist of authorized users—referred to as "securing" the access point.[dubious – discuss]
Wikinews has related news: Florida man charged with stealing WiFi
Measures to deter unauthorized users include suppressing the AP's SSID broadcast, allowing only computers with known MAC addresses to join the network, and various encryption standards. Suppressed SSID and MAC filtering are ineffective security methods as the SSID is broadcast in the open in response to a client SSID query and a MAC address can easily be spoofed. If the eavesdropper has the ability to change his MAC address, then he can potentially join the network by spoofing an authorized address.
WEP encryption can protect against casual snooping, but may also produce a misguided sense of security since freely available tools such as AirSnort or aircrack can quickly recover WEP encryption keys. Once it has seen 5-10 million encrypted packets, AirSnort can determine the encryption password in under a second;[14] newer tools such as aircrack-ptw can use Klein's attack to crack a WEP key with a 50% success rate using only 40,000 packets. The newer Wi-Fi Protected Access (WPA) and IEEE 802.11i (WPA2) encryption standards resolve most of the serious weaknesses of WEP encryption.
Attackers who have gained access to a Wi-Fi network can use DNS spoofing attacks very effectively against any other user of the network, because they can see the DNS requests made, and often respond with a spoofed answer before the queried DNS server has a chance to reply.
One serious issue with wireless network security is not just encryption, but access to the network (signal reception). With wired networking it is necessary to get past either a firewall or the security guard & locked doors. With wireless it is necessary only to get reception and spend as long as you want, comfortably out of (easy) reach of the network owner. Most business networks protect sensitive data and systems by attempting to disallow external access. Thus being able to get wireless reception (and thus possibly break the encryption) becomes an attack vector on the network as well.
Recreational logging and mapping of other people's access points has become known as wardriving. It is also common for people to use open (unencrypted) Wi-Fi networks as a free service, termed piggybacking. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. 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. In a Florida court case, owner laziness was determined not to be a valid excuse. [17]
Piggybacking is often unintentional. Most access points are configured without encryption by default, and operating systems such as Windows XP SP2 and Mac OS X may be configured to automatically connect 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's signal is stronger. 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 insecure network to login to a website, thereby making the login credentials available to anyone listening, if the website is using an insecure protocol like HTTP, rather than a secure protocol like HTTPS.
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