▁device ▁or ▁stack , ▁sometimes ▁in ▁conj unction ▁with ▁an ▁up stream ▁provider ▁performing ▁additional ▁filtering . ▁The ▁following ▁content - control ▁techn ologies ▁have ▁been ▁confirmed ▁to ▁be ▁used ▁to ▁implement ▁all ▁types ▁of ▁web ▁blocking ▁( includes ▁virtual ▁operators ): ▁ ▁R ules pace ▁and ▁O 2 ▁are ▁the ▁only ▁known ▁services ▁with ▁a ▁public ▁categor isation ▁and ▁blocking ▁check ▁tool . ▁ ▁By ▁feed ▁type ▁ ▁Circ um vention ▁▁ ▁Site ▁blocks ▁can ▁be ▁circum vent ed ▁using ▁method ▁trivial ▁through ▁to ▁complex ▁such ▁as ▁use ▁of ▁Tor , ▁V PN s , ▁site ▁specific ▁and ▁general ▁web ▁pro x ies , ▁and ▁other ▁circum vention ▁techniques . ▁ ▁Child ▁ab use ▁image ▁content ▁list ▁ ▁Due ▁to ▁the ▁proxy ▁server ▁implementation ▁of ▁the ▁I WF ' s ▁child ▁ab use ▁image ▁content ▁list ▁( form ally ▁C lean feed ) ▁system , ▁websites ▁that ▁filter ▁users ▁by ▁IP ▁address , ▁such ▁as ▁w ik is ▁and ▁file ▁lock ers , ▁will ▁be ▁significantly ▁broken , ▁even ▁if ▁only ▁a ▁tiny ▁proportion ▁of ▁its ▁content ▁is ▁flag ged . ▁ ▁Copy right ▁ ▁In ▁response ▁to ▁the ▁increasing ▁number ▁of ▁file ▁sharing ▁related ▁blocks , ▁a ▁number ▁of ▁proxy ▁aggreg ator ▁sites , ▁e . g . ▁tor rent pro x ies . com , ▁have ▁become ▁popular . ▁In ▁addition ▁to ▁the ▁following , ▁proxy ▁sites ▁designed ▁to ▁circum vent ▁blocks ▁have ▁been ▁secret ly ▁blocked ▁by ▁I SP s , ▁driving ▁users ▁to ▁proxy ▁comparison ▁sites . ▁The