Title I of the U.S. DMCA, the WIPO Copyright and Performances and Phonograms Treaties Implementation Act has provisions that prevent persons from "circumvent[ing] a technological measure that effectively controls access to a work". Thus if a distributor of copyrighted works has some kind of software, dongle or password access device installed in instances of the work, any attempt to bypass such a copy protection scheme may be actionable – though the US Copyright Office is currently reviewing anticircumvention rulemaking under DMCA – anticircumvention exemptions that have been in place under the DMCA include those in software designed to filter websites that are generally seen to be inefficient (child safety and public library website filtering software) and the circumvention of copy protection mechanisms that have malfunctioned, have caused the instance of the work to become inoperable or which are no longer supported by their manufacturers.
What are adult safety and public library software used to filter? (If the question is unanswerable, say "unanswerable")
unanswerable