Leech (computing)

In computing and specifically on the Internet, being a leech or leecher refers to the practice of benefiting, usually deliberately, from others' information or effort but not offering anything in return, or only token offerings in an attempt to avoid being called a leech. In economics this type of behavior is called "Free riding" and is associated with the Free rider problem.

The name derives from the leech, an animal which sucks blood and then tries to leave unnoticed. Other terms are used, such as freeloader, but leech is the most common.


* Wi-Fi leeches attach to open wireless networks without the owner's knowledge or permission in order to access the Internet. Typical examples of this might include someone who connects to a neighbor's open access point, or someone who connects to a café's free wireless service from their car in the parking lot. This form of leeching in particular is the subject of much legal and ethical debate.

* Direct linking is a form of bandwidth leeching that occurs when placing an unauthorized linked object, often an image, from one site in a web page belonging to a second site (the leech).

* In most P2P-networks, leeching can be defined as behavior consisting of downloading more data, over time, than the individual is uploading to other clients, thus draining speed from the network. The term is used in a similar way for shared FTP directories. Mainly, leeching is taking without giving.

* Claiming credit for, or offering for sale, freely available mobile phone themes, wallpapers, ringtones, etc., which have been created and uploaded by others to the Internet.

* By [http://phd.kt.pri.ee/2008/09/09/parasitic-computing/ leech computing] one might refer to the somewhat esoteric, yet fun idea of stealing CPU cycles from unknowing users via specially crafted webpages or viruses.


* Wi-Fi networks can implement various authentication and access control technologies in order to prevent leeching. The most common are client MAC address authorization tables, Wired Equivalent Privacy, and Wi-Fi Protected Access.
* Bandwidth leeching can be prevented by running an anti-leeching script on the website's server. It can automatically ban IPs that leech, or can redirect them to faulty files.


Among users of the BitTorrent file distribution protocol, a leech is a user who disconnects as soon as he/she has a complete copy of a particular file. However, most sites prefer the term leecher for all users who are not seeders (don't have the complete file yet). However, because BitTorrent clients usually begin to upload files almost as soon as they have started to download them, such users are usually not freeloaders. Therefore this kind of leeching is considered to be a legitimate practice. Reaching an upload/download ratio of 1:1 (meaning that the user has uploaded as much as he/she has downloaded) in a BitTorrent client is considered a minimum in the etiquette of that network. A leech becomes a seeder (A provider of the file) when he or she finished downloading and continues to run the client. They will remain a seeder until the file is removed or destroyed.

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