Technological protection measure (TPM) may also be referred to as digital locks. Included in this are devices, technology, or a digital component of a file that is placed on a work (ebooks, songs, video) by the copyright holder to restrict the use of the work.
For instance, when downloading eBooks from the library the books will contain a DRM component which enables you to usse the book for the duration of your checkout period, but will restrict use following the due date of the item.
It is an infringement of copyright to bypass any such TPM, or offer a service which enables others to circumvent a TPM.
For additional information about TPMs and digital locks check out the TPMs/Digital Locks information at http://www.2learn.ca/ydp/copylocks.aspx