BitTorrent　is　vulnerable　to　several　attacks,　since　the　protocol　initially　designed　lacks　of　security　concerns.　Although　researches　and　studies　have　recently　paid　lots　of　attentions　on　security　issues　with　BitTorrent,　a　leak　in　meta　file　has　not　been　on　the　agenda　yet.　In　this　paper　we　analyze　the　design　principle　of　BitTorrent　meta　file　and　show　the　leak　which　can　cause　arbitrary　data　modification　of　unprotected　section,　especially　the　tracker　list.　We　show　how　attacker　injects　malicious　trackers　and　peers　into　BitTorrent　by　exploiting　such　leak　and　some　major　threats　BitTorrent　suffers　from　the　injection　behavior.　In　order　to　fix　the　leak,　we　propose　an　approach　which　puts　the　fingerprint　of　key　data　in　the　meta　file　info　dictionary.　Experimental　results　show　that　the　fingerprint　can　prevent　malicious　tracker　injection　from　modifying　meta　file.　Results　also　show　the　network　environment　of　unmodified　file　can　be　protected　though　attacker　may　forge　fingerprint.　©　2011　IEEE.