Theft is defined as as the act of stealing. Stealing is the taking of property, goods, and services for which the person didn't pay.
      Bandwidth is the amount of data that can be passed along a communications channel in a given period of time. Websites such as this one are hosted at sites which permit only so much bandwidth to be used within a period of time, usually a month. Once this bandwidth has been reached, no more information can be transferred until the following month with the exception of hosts who provide more bandwidth per month at an additional cost to the account holder.
      The most common form of bandwidth theft occurs when someone links directly to an image at another website so that image appears at their website without them having to download the image to their service. People do this so they can save storage space at their service. In other words, they get free access to a service for which someone else is paying. Unless the owner of the website gives you permission to link directly to the image, you're stealing.
      The person holding the website account can access the data telling them whether or not someone is illegally linked to their images and other material. This information appears in a section of the account which lists all access to the website. Such information includes the URL of the referring site such as a search engine or a link from another website. When the URL provided is accessing only an image (specified by the name of the image folder) and not a specific page, the owner knows the page at which the image appears contains a link directly to the image. Any and all information within these logs are accepted as proof of theft and the owner can initiate legal proceedings.
      The only time it's legal to link directly to an image and utilize the bandwidth at another website is by requesting and receiving permission from the site owner to do so. If you don't get permission, don't link to those images.
      A common misconception is that if an image appears in an image search at a search engine it's free to use at your website. Even if the search engine shows the image, it's the responsibility of the person wanting to use the image to get permission from the owner. When the images do appear, the search engine usually provides the URL to that image in the image subfolder at the website. This doesn't mean you can use that URL so the image appears at your site. If you do so without the permission of the site owner, you're stealing their bandwidth and open to legal actions taken against you.
      The use of someone else's bandwidth to connect to images is also a violation of copyright laws. When you use the images at your site without permission, you're using copyrighted material you don't own. So, not only can you be sued for the use of the bandwidth, you'll most likely get hit with a suit for violation of copyright.
      Do I really need to tell you bandwidth theft isn't worth the final costs of a lawsuit?