K thut tn cng XSSXSS l g?XSS l t vit tt ca Cross-Site Scripting l mt k thut tn cng bng cch chn vo cc website ng (ASP, PHP, CGI, JSP ...) nhng th HTML hay nhng on m script nguy him.Trong nhng on m nguy him c chn vo hu ht c vit bng Client-Site Script nh javascript, Jscript, DHTML v cng c th l cc th HTML.XSS l mt li ph bin, c rt nhiu trang web b mc phi li ny, chnh v th ngy cng c nhiu ngi quan tm n li ny.Truy tm l hng XSS ca webCch 1: S dng nhiu chng trnh d qut li ca ng dng web, v d nh chng trnh Web Vulnerability Scanner d qut li XSS.Cch 2: Thc hin 5 bc:Bc 1: M website cn kim traBc 2: Xc nh cc ch (phn) cn kim tra XSS. 1 Site bt k bao gi cng c cc phn:Search, error message, web form. Ch yu li XSS nm phn ny, ni chung XSS c th xy ra ch no m ngi dng c th nhp d liu vo v sau nhn c mt ci g . V d chng ta nhp vo chui XSSBc 3: Xc minh kh nng site c b li XSS hay khng bng cch xem cc thng tin tr vBc 4: Khi xc nh ch c kh nng b dnh li XSS th chng ta s chn nhng on code ca chng ta vo th tipBc 5: Ln k hoch kch bn tn cngTn cngTht ra th c rt nhiu k thut tn cng da trn li XSS ny, ch yu l sau khi bit cch tm l hng th mi ngi s c mt mu m cho cch tn cng ca mnh. y mnh xin gii thiu n cc bn mt k thut m mnh thc hin thnh cng trn trang moodle ca khoa cng ngh thng tin KHTN. K thut n cp password.

Sau khi xc minh mt iu chc chn rng trang moodle b li XSS ch ng nhp. Ti lp tc vit ngay mt ng dng nh ri up ln mt ci host free, ng dng ny s c nhim v nhn thng tin v mssv v password gi v v ghi xung file txt. Cn nhn th no th mi cc bn xem tip...

Sau :Bc 1: Ti to mt mail gi dng ni l: Din n tuyn dng ca Intel, mi cc bn no quan tm th tham gia.Ri to ra mt ci ng link gi: nhng ti l reference n ti mt ci trang gi ca tui. Trong tch tc trang ny s gn mt ci on script c c nhim v ly v username v password sau khi ng nhp v gn vo ci trang tht(V trang tht b li XSS nn cho php chng ta gn m c ln, gn y c ngha l khi chng ta view source code ca trang ln, chng ta s thy c mt on script ca chng ta nm u ), ri sau redirect sang trang tht ngay lp tc khi b nghi ng.

Bc 2: Ngi dng vo mail, tng tht, click vo link v thy chy ng trang moodle (H u ng rng, trang tht b gn m c ln, trong thi gian qu nhanh nn h khng nghi ng g c, nhng nu ai s thy link khng ng).

Bc 3: H ng nhp, khi ng dng s chy bin dch t trn xung, v tt nhin s chy lun c script m chng ta ci, khi MSSV v password s c ly v gi cho mt ci trang trn server m chng ta dng ra.

Bc 4: ng dng server ca ta nhn c mssv v password, ghi ra file txt.

Bc 5: Kt thc qu trnh tn cng, chng ta c mt danh sch cc ti khon ca sinh vinPhng chngNh cp trn, mt tn cng XSS ch thc hin c khi gi mt trang web cho trnh duyt web ca nn nhn c km theo m script c ca k tn cng. V vy nhng ngi pht trin web c th bo v website ca mnh khi b li dng thng qua nhng tn cng XSS ny, m bo nhng trang pht sinh ng khng cha cc tag ca script bng cch lc v xc nhn hp l cc d liu u vo t pha ngi dng hoc m ha(endcoding) v lc cc gi tr xut cho ngi dng.

LcLun lun lc cc d liu nhp t pha ngi dng bng cch lc cc k t meta (k t c bit) c nh ngha trong c t ca HTML. Mi trng nhp liu bao gm c tham s lin kt s c kim tra pht hin cc th script.

M haLi XSS c th trnh c khi my ch Web m bo nhng trang pht sinh c m ha (encoding) thch hp ngn chy chy cc script khng mong mun.M ha pha my ch l mt tin trnh m tt c ni dung pht sinh ng s i qua mt hm m ha ni m cc th script s c thay th bi m ca n.Ni chung, vic m ha(encoding) c khuyn khch s dng v n khng yu cu bn phi a ra quyt nh nhng k t no l hp l hoc khng hp l.Tuy nhin vic m ha tt c d liu khng ng tin cy c th tn ti nguyn v nh hng n kh nng thc thi ca mt s my chPhm vi v tnh kh thi ca phng php tn cng bng XSSM JavaScript c c th truy cp bt c thng tin no sau y: Cookie c nh (ca site b li XSS) c duy tr bi trnh duyt. RAM Cookie (ca site b li XSS) Tn ca tt c cc ca s c m t site b li XSS Bt c thng tin m c th truy cp c t DOM hin ti (nh value, m HTML)