ford ▁University ▁and ▁Jan ▁Ped ers en ▁of ▁Y ahoo ! ▁in ▁their ▁paper ▁" Com b ating ▁Web ▁Sp am ▁with ▁Trust R ank " ▁in ▁ 2 0 0 4 . ▁Today , ▁this ▁algorithm ▁is ▁a ▁part ▁of ▁major ▁web ▁search ▁engines ▁like ▁Y ahoo ! ▁and ▁Google . ▁▁ ▁One ▁of ▁the ▁most ▁important ▁factors ▁that ▁help ▁web ▁search ▁engine ▁determine ▁the ▁quality ▁of ▁a ▁web ▁page ▁when ▁returning ▁results ▁are ▁back links . ▁Search ▁engines ▁take ▁a ▁number ▁and ▁quality ▁of ▁back links ▁into ▁consideration ▁when ▁assigning ▁a ▁place ▁to ▁a ▁certain ▁web ▁page ▁in ▁SER P s . ▁Many ▁web ▁sp am ▁pages ▁are ▁created ▁only ▁with ▁the ▁intention ▁of ▁mis leading ▁search ▁engines . ▁These ▁pages , ▁chief ly ▁created ▁for ▁commercial ▁reasons , ▁use ▁various ▁techniques ▁to ▁achieve ▁higher - than - des erved ▁rank ings ▁in ▁the ▁search ▁engines ' ▁result ▁pages . ▁While ▁human ▁exper ts ▁can ▁easily ▁identify ▁sp am , ▁search ▁engines ▁are ▁still ▁being ▁improved ▁daily ▁in ▁order ▁to ▁do ▁it ▁without ▁help ▁of ▁humans . ▁▁ ▁One ▁popular ▁method ▁for ▁impro ving ▁rank ings ▁is ▁to ▁increase ▁the ▁perce ived ▁importance ▁of ▁a ▁document ▁through ▁complex ▁linking ▁schemes . ▁ ▁Google ' s ▁Page R ank ▁and ▁other ▁search ▁ranking ▁algorithms ▁have ▁been ▁subject ed ▁to ▁such ▁manip ulation . ▁ ▁Trust R ank ▁see ks ▁to ▁combat ▁sp am ▁by ▁filtering ▁the ▁web ▁based ▁upon ▁reli ability . ▁The ▁method ▁calls ▁for ▁selecting ▁a ▁small ▁set ▁of ▁seed