Nhu da noi tir dau toan hoc thong ké dong vai tro rat quan trong trong trong moi tinh vuc. Thong ké gnp cho viec mm bat diinh gin tinh hinh tro ten truc quan va de
hie“u hon. Xu 1y va 6ng d g dit 1ie(u thong ké dem lai hieu qu:i 1éin lao nong viec tién do:in va tir do co the xay dijrig ten mot he dong hoa hoat dong chinh xac. Hir6ng tiép elm thong ké theo ly thuyet Bayes kh:i don gun nhung dem lai hie(u qua rat cao chinh vI the ma no duoc mug d g kha pho biéu trong hau he't cac tinh vuc.
So véii ciic phuong phap khiic, phuong phiip thong ké Bayes lap 1ua)n theo kinh nghiem dope tich thy up dung vao mo hinh phan loai doi tupng tinh hoat hon, phu hpp vol dac mang cua bai toén hon. Cac cc ché me tuong cung gan gin véii cach suy 1ua( n thong thiréing chinh vi vay ma cac két qua phfin loai tuong doi giong véii cach phfin loai thong thu6ng.
Cut ket qua da dat dupc la:
Khoii 1ua( n da tap trung nghién emu ve 1y thuyet Bayes, tir bucrc cc so do tim hie“u tiép ve“ mot ring dung cua no tién quan truc tiép den nganh cong nghe thong tin do la Eng dung loc thu rac. Qua trinh tim hieu ve nguyén 1y va cach thuc hoat dong cua bo loc da rfit ra dupc nhung ket 1ua( n ve uu nhircic diem ctia tiép can thong ké Bayes trong viec phan loai thu riic. Doi voi van de ting dung thuc té, khoa 1ua)n su dung plugin BayesSpam nhu mot doi tuong chinh de tim hie“u va nghién elm. Doi véii van de ap dung ly thuyet Bayes, khoii 1ua)n nghién cfiu xay djmg cac cong thuc tinh xac suat sao cho viec xu 1y thong tin ncr ten nhanh gon va co do chinh xac cao.
Tir vie(c tim hieu ting dung BayesSpam, khoa 1ua) n da rfit ra diroc mot so nhan dinh ve uu diem va nhircic diem cua
bo) loc nong quit trinh hoat dong. Két quit phan loai thu rac nhin chung la gan giong voi cac ke't qua danh gin thu boi ngu i dung.
Tuy nhién, do thoi gian co han cling nhu cac kien thuc chuyén “n ve he thong thu dien tir nén cac két 1ua) n riit ra dupc trong qua trinh nghién ciii co nhiéu han ché. Duoi day la nhrng uu nhuoc diem chinh cua bo loc thu rac Bayes.
Nhimg uu diem chinh:
> Uu diem cua bo loc thu rac Bayes do la no co the dirpc hua luyen boi chinh nguoi dung cc so. Day co the the noi la uu diem 1éin nhat, no tao ra dupc net dac trirng ve“ cach nhin nhfin thir rac ciia 'i nguoi dung. Thuat toan Bayes va ting dung
Cut thu rite ma mot nguoi dung nha)n dupe thuéng tién quan toi cue hoat dong trpc tuyen ctia ngucri dung. Vi du, mot nguoi sit d9ng co the da dupe dang v:to mot ban tin true tuye'n ma nguoi sit dpng xem xét
nhu la thu rite. Dang xem thong tin my co the chira cue tit ngit dupe pho bién cho tat ca cue bén tin, chang han nhu te“n ciia ban tin va nguon goc ciia no dia chi email. Bo loc thu rac Bayesian sé chi dinh mot xiic sufit cao hon dua trén ciich nhin nhan ciia nguéii sit d;ing. Thu dien thti hpp phiip sé nh°an dupe chin nhan theo xu huéing khiic
“n , te’n
ty ciia ban va ten ciia khiich hang sé dupe de“ cap thufing xuyén. C:ie bp lpc sé chi dinh mot thu rite xac suat thap hon cho cue email co chua cac ten do.
Xiic sufit ciia c:ie tit la duy nhat doi véii moi ngitéii dung va co the 1éin theo thoi gian h luyen, citng véri su hieu chinh viec hua 1uye(n 'i khi co thu loc sai. Két qua la, loc thu r:ie Bayesian tiing do chinh xiic khi dupe dao tao thuéing xuye’n theo cue guy tae dupe x:ie dinh
nhupc dure chinh:
Mot thu(at dupe sts d;;ng bcii Spammer nham
gum tinh
hieu quit ciia bo loc thu rite la dua vao chinh nguye“n tae hoat dong ciia no. Ki thua)t my sé che’n cue ti rné khong phiii la binh thuéing tién ke't véii cue noi dung spam voi v® bin hpp phap (thu th)ap tit cue nguon tin tire hpp ph:ip hay viin chuong). Do do gi:inn gin tri. x:ie sufit két hpp ciia thu dien tit la thu rite, tain cho no céng co nhiéu kha ‘ g vupt qua bo loc thu rite Bayes.
Mot ½ thiuit khiic dupe sit d;ing de che it bo loc thu rite Bayes dé› la thay the cue van ban bang hinh énh, hoac true tie'p da)t 1ie’n ke't chira n(oi dung spam den hinh énh. Toén bo npi dung ciia tin nhan, hoac mot so phfin cua no, dupe thay the béng mot hinh tinh co cung
mot n(oi dung dupe trinh bay Hi cuo nguéii xem. Bo loc thu rite thuéing khong the phfin tich hinh énh n:iy, ma co the’ chua cue tit nhay c:inn
nhu "khiéu dim". Tuy nhién, nhiéu he thong thu dien tit da vo hieu hon Thu(at toiin Bayes va ring d
miin hinh hien th] cua tién két hinh énh vi 1y do bio m°at, nhung cue spammer lai
gtd 1i“en ket de'n hinh anh ci xa co the
tie'p muc tiéu spam it
hon. Ngoai ra, mot hinh anh co kich thuoc 1éin hon kich thuoc tuong duong ciia viin bin. Do dé›, cue spammer cm nliiéu hon nhu cau bring thong de’ gin tin nh¾ true tiép bao gore ca hinh anh.
Thu(at toiin Bayes va ring d rig
Do vay, sau buoc tim hieu 1y thuyet va ting d;ing thi hudng nghién ciii tiép ctia de tai nh ting hieu quit loc la:
Tim ra ciii nhin chung ve thu rite ciia nhung nguéii dung thu song cung he thong thu dien tir. Bring ciich riit ra nhimg email co xiic suat la thu rac cao de bo xung vao ta“p hua tuyén chung cho tat ca moi nguoi nh gia tiing kinh nghiem cho bo lpc.
Ngiin chiin vi(ec Spam bang hinh anh bring vi(ec dna ra thong biro la thu rac néu no co n(oi dung chu ye'u la do hoa. Don gun nhat la khong cho hien th] hinh tinh khi nguéii dung duyet thu trii khi ho co nhu cau xem hinh anh thi tu hp sé b°at hien thi.
Tich hpp phan tich hinh :inh de lay ra viin ban song hinh nham gum vi(ec lpc sai do loai bo ta“t ca thu co noi dung chit yeu do hoa. Viec my doi hoi he thong phai ma.nh cung thua)t toiin phfin tich hinh énh thong
Bo xung them vao ta“p cue tit trung tinh tieng Viet cho bo lpc nham tang toe va tie't kiém tai nguyén cho cc sci dii lieu. Vi dq nhu cue lii trung tinh tieng viét ring voi cue tit trung tinh tieng Anh nhu: thi, la, o, ciii, con, va, hoac, .
[1] Nguyen Quoc Dai, JQ Thuyét Bayes, mang Bayes. (2009)
[2] Nguyen Thanh Son, Le Khénh Lua)n; Jj thuyét xéc suit va thcing ké toan ;
Nxb Thong ke“ (2008)
[3] Nguyen Duy Tién, Tran Minh Ngoc Dat hoc Khoa Hoc Tir Nhién, DHQGHN, Bai giang cua Vién Thong Ké Thé Gioi IMS Lai Malaysia
[4] Azam. N, Dar. H. A, Marwat. S; Comparative study on Feature Space Reduction for Spam Detection
[5] Paul Graham; A plan for spam 2092. Xem tai dia chi
http://pau1graham. com/spam.html
[6] Wikipedia , Bayesian Spam Filtering. Xem tai dia chi
http://en.wikiped1a.org/wiki/Ba v esian spam filtering
[7] Wikipedia , Sequential Bayesian Filtering. Xem tai d]a chi
http://en.wikiped1a.org/wiki/Seq uential bayesian filtering Thu(at toiin Bayes va mug