As part of the U.S. Copyright Office's DMCA rulemaking procedure (under which it identifies non-infringing uses that are hampered by the DMCA), the Office has twice issued an exemption for circumvention of filtering software programs in order to identify the list of sites included within the program. Filtering programs can be used to filter or block inappropriate material, yet the same programs have been subject to considerable criticism over concerns that they may be overbroad and block perfectly legitimate material. The only way for a party to ascertain whether their site is included on the block list is to access the lists contained in the software program, a process that typically requires circumvention.
In 2000, the Copyright Office found that an exception for filtering programs was needed. It reaffirmed the decision in 2003. In 2006, Seth Finklestein, the primary supporter of the "censorware" exception abandoned the fight for another renewal and the exception was dropped. The same concerns remain, however, which is why a clear exception for the circumvention of filtering programs is needed within Bill C-61.