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What Does Leech Mean?

In computing, generally, a leech is an individual who drains resources, bandwidth, or data off a website or a network, often in an unethical manner. This term is often used in the context of peer-to-peer (P2P) networks. Here, a leech refers to an individual who downloads the files or data without uploading anything in exchange.


Such a person is also known as a leecher.

Techopedia Explains Leech

The computing term leech is a derived from the pesky animal found in lakes, which attaches to their hosts and sucks blood. Leeching is not necessarily an illegal consumption of computer resources; rather, it refers to using an excessive amount of a resources without giving anything back. For example, in USENET newsgroups, leeching is not considered unethical as the newsgroup protocol does not imply equal sharing of data. People are free to download any file without sharing the same to other users. A P2P network is different — there is an unwritten code that if you download, you should also share your resources so that others can also make use of the data.

Other examples of leechers include:

  • In Wi-Fi, a leecher is somebody who attaches his wireless device to an open wireless network to access the Internet without the knowledge of the Wi-Fi owner. In most countries, accessing a network in this fashion is illegal.
  • In bandwidth leeching, a leecher creates a direct link to an object from a 3rd party server, usually an image, and displays it on their own website.

In order to prevent Wi-Fi leeching, the Wi-Fi networks can use multiple access control and authentication technologies. One of the most effective and widely used technologies used to prevent leeching is Wi-Fi Protected Access (WPA).

In order to prevent the bandwidth leeching, the users have to run anti-leeching scripts on their website’s server. This automatically bans the IPs that attempts to leech, or redirects those leechers to defective files.


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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.