Cc c ch chng Spam Mail

Spam gy ra rt nhiu tc hi, do vy vic phng chng v ngn chn cc spam l cn thit. Hin c nhiu cng ty phn mm cung cp gii php chng spam, mi dng sn phm c nhng tnh nng v cc u nhc im ring, nhng hu ht cc sn phm u hot ng da vo mt s nguyn l sau:

S dng DNS blacklist

Phng php s dng DNS black list s chn cc email n t cc a ch nm trong danh sch DNS blacklist. C hai loi danh sch DNS Blacklist thng c s dng, l:

Danh sch cc min gi spam bit, danh sch cc min ny c lit k v cp nht ti a chhttp://spamhaus.org/sbl.

Danh sch cc my ch email cho php hoc b li dng thc hin vic chuyn tip spam c gi i t spammer. Danh sch ny c lit k v cp nht thng xuyn ti a chhttp://www.ordb.org. C s d liu Open Relay Database ny c duy tr bi ORDB.org l mt t chc phi li nhun.

Khi mt email c gi i, n s i qua mt s SMTP server trc khi chuyn ti a ch ngi nhn. a ch IP ca cc SMTP server m email chuyn qua c ghi trong phn header ca email. Cc chng trnh chng spam s kim tra tt c cc a ch IP c tm thy trong phn header ca email sau so snh vi c s d liu DNS Blacklist bit. Nu a ch IP tm thy trong phn ny c trong c s d liu v cc DNS Blacklist, n s b coi l spam, cn nu khng, email s c coi l mt email hp l.

Phng php ny c u im l cc email c th c kim tra trc khi ti xung, do tit kim c bng thng ng truyn. Nhc im ca phng php ny l khng pht hin ra c nhng email gi mo a ch ngi gi.

S dng SURBL list

Phng php s dng SURBL pht hin spam da vo ni dung ca email. Chng trnh chng spam s phn tch ni dung ca email xem bn trong n c cha cc lin kt c lit k trong Spam URI Realtime Blocklists (SURBL) hay khng. SURBL cha danh sch cc min v a ch ca cc spammer bit. C s d liu ny c cung cp v cp nht thng xuyn ti a chwww.surbl.org..

C nhiu danh sch SURBL khc nhau nh sc.surbl.org, ws.surbl.org, ob.surbl.org, ab.surbl.org..., cc danh sch ny c cp nht t nhiu ngun. Thng thng, ngi qun tr thng kt hp cc SURBL list bng cch tham chiu ti a ch multi.surbl.org. Nu mt email sau khi kim tra ni dung c cha cc lin kt c ch ra trong SURBL list th n s c nh du l spam email, cn khng n s c cho l mt email thng thng.

Phng php ny c u im pht hin c cc email gi mo a ch ngi gi nh la cc b lc. Nhc im ca n l email phi c ti xung trc khi tin hnh kim tra, do s chim bng thng ng truyn v ti nguyn ca my tnh phn tch cc ni dung email.

Kim tra ngi nhn

Tn cng spam kiu t in s dng cc a ch email v tn min bit to ra cc a ch email hp l khc. Bng k thut ny spammer c th gi spam ti cc a ch email c sinh ra mt cch ngu nhin. Mt s a ch email trong s c thc, tuy nhin mt lng ln trong l a ch khng tn ti v chng gy ra hin tng lt cc my ch mail.

Phng php kim tra ngi nhn s ngn chn kiu tn cng ny bng cch chn li cc email gi ti cc a ch khng tn ti trn Active Directory hoc trn my ch mail server trong cng ty. Tnh nng ny s s dng Active Directory hoc LDAP server xc minh cc a ch ngi nhn c tn ti hay khng. Nu s a ch ngi nhn khng tn ti vt qu mt ngng no (do ngi qun tr thit lp) th email gi ti s b coi l spam v chn li.

Kim tra a ch

Bng cch kim tra a ch ngi gi v ngi nhn, phn ln spam s c pht hin v chn li. Thc hin kim tra a ch ngi gi trc khi email c ti xung s tit kim c bng thng ng truyn cho ton h thng.

K thut Sender Policy Framework (SPF,www.openspf.org) c s dng kim tra a ch ngi gi email. K thut SPF cho php ch s hu ca mt tn min Internet s dng cc bn ghi DNS c bit (gi l bn ghi SPF) ch r cc my c dng gi email t min ca h. Khi mt email c gi ti, b lc SPF s phn tch cc thng tin trong trng From hoc Sender kim tra a ch ngi gi. Sau SPF s i chiu a ch vi cc thng tin c cng b trong bn ghi SPF ca min xem my gi email c c php gi email hay khng. Nu email n t mt server khng c trong bn ghi SPF m min cng b th email b coi l gi mo.

Chn IP

Phng php ny s chn cc email c gi n t cc a ch IP bit trc. Khi mt email n, b lc s phn tch a ch my gi v so snh vi danh sch a ch b chn. Nu email n t mt my c a ch trong danh sch ny th n s b coi l spam, ngc li n s c coi l email hp l.

S dng b lc Bayesian

B lc Bayesian hot ng da trn nh l Bayes tnh ton xc sut xy ra mt s kin da vo nhng s kin xy ra trc . K thut tng t nh vy c s dng phn loi spam. Nu mt s phn vn bn xut hin thng xuyn trong cc spam nhng thng khng xut hin trong cc email thng thng, th c th kt lun rng email l spam.

Trc khi c th lc email bng b lc Bayesian, ngi dng cn to ra c s d liu t kha v du hiu (nh l k hiu $, a ch IP v cc min...) su tm t cc spam v cc email khng hp l khc.

Mi t hoc mi du hiu s c cho mt gi tr xc sut xut hin, gi tr ny da trn vic tnh ton c bao nhiu t thng hay s dng trong spam, m trong cc email hp l thng khng s dng. Vic tnh ton ny c thc hin bng cch phn tch nhng email gi i ca ngi dng v phn tch cc kiu spam bit.

b lc Bayesian hot ng chnh xc v c hiu qu cao, cn phi to ra c s d liu v cc email thng thng v spam ph hp vi c th kinh doanh ca tng cng ty. C s d liu ny c hnh thnh khi b lc tri qua giai on hun luyn. Ngi qun tr phi cung cp khong 1000 email thng thng v 1000 spam b lc phn tch to ra c s d liu cho ring n.

S dng danh sch Black/white list

Vic s dng cc danh sch black list, white list gip cho vic lc spam hiu qu hn.

Black list l c s d liu cc a ch email v cc min m bn khng bao gi mun nhn cc email t . Cc email gi ti t cc a ch ny s b nh du l spam.

White list l c s d liu cc a ch email v cc min m bn mong mun nhn email t . Nu cc email c gi n t nhng a ch nm trong danh sch ny th chng lun c cho qua.

Thng thng cc b lc c tnh nng t hc, khi mt email b nh du l spam th a ch ngi gi s c t ng a vo danh sch black list. Ngc li, khi mt email c gi i t trong cng ty th a ch ngi nhn s c t ng a vo danh sch white list.

Kim tra Header

Phng php ny s phn tch cc trng trong phn header ca email nh gi email l email thng thng hay l spam. Spam thng c mt s c im nh:

trng trng From: hoc trng To:

Trng From: cha a ch email khng tun theo cc chun RFC.

Cc URL trong phn header v phn thn ca message c cha a ch IP c m ha di dng h hex/oct hoc c s kt hp theo dng username/password (v d cc a ch:http://00722353893457472/hello.com,www.citibank.com@scammer.com)

Phn tiu ca email c th cha a ch email ngi nhn c nhn ha email . Lu khi s dng tnh nng ny vi cc a ch email dng chung c dng nhsales@company.com. V d khi mt khch hng phn hi bng cch s dng tnh nng auto-reply vi tiu your email to sales c th b nh du l spam

Gi ti mt s lng rt ln ngi nhn khc nhau.

Ch cha nhng file nh m khng cha cc t nh la cc b lc.

S dng ngn ng khc vi ngn ng m ngi nhn ang s dng.

Da vo nhng c im ny ca spam, cc b lc c th lc chn.

S dng tnh nng Challenge/Response

Tnh nng ny s yu cu ngi ln u gi email xc nhn li email u tin m h gi, sau khi xc nhn, a ch email ca ngi gi c b sung vo danh sch White list v t tr v sau cc email c gi t a ch c t ng cho qua cc b lc.

Do spammer s dng cc chng trnh gi email t ng v h khng th xc nhn li tt c cc email gi i, v th nhng email khng c xc nhn s b coi l spam.

Phng php ny c hn ch l n yu cu nhng ngi gi mi phi xc nhn li email u tin m h gi. khc phc nhc im ny, ngi qun tr ch nn s dng phng php ny i vi nhng email m h nghi ng l spam.

PHNG TRNH TH RC

Ngoi vic s dng cc b lc chng spam, ngi s dng cng ng vai tr quan trng trong vic chng li i dch th rc. Bi vy ngi dng cn tun theo mt s nguyn tc sau:

Lun cp nht cc bn v mi nht ca cc phn mm ang ci t trn my.

m bo tt c cc my lun c cp nht cc phn mm chng virus v chng spam.

S dng cc firewall bo v h thng.

Khng tr li cc email l khng r ngun gc. i vi cc spammer, khi nhn c mt tr li t hng ngn email h gi i th cng chng minh l phng php c hiu qu. Ngoi ra, vic tr li li cn xc nhn l a ch email ca bn l c thc v hin ang c s dng. Do vy a ch email ca bn s ng gi hn, v cc spammer s gi nhiu th rc hn.

Khng gi cc thng tin c nhn ca bn (s th tn dng, mt khu, ti khon ngn hng, v.v... ) trong th in t. Cc spammer v nhng k la o qua mng c th to ra nhng trang web gi mo cc t chc, ngn hng... ngh bn gi mt khu v mt s thng tin v th tn dng ca bn qua email.

Khng hi p email bng cch nhn ln t nh loi b (remove) hoc ngng ng k (unsubscribe) trong dng tiu hoc trong ni dung ca th tr khi y l ngun ng tin cy (cc email tip th trc tip). y l tiu xo ca cc spammer ngi s dng hi p li cc spam ca h. Khi nhn c hi p, cc spammer khng nhng khng loi b a ch email ca bn ra khi danh sch m cn gi ti nhiu spam hn bi v h bit rng a ch email ca bn hin ang hot ng.

Khng bao gi bm vo cc lin kt URL hoc a ch trang web c ghi trong spam ngay c khi n hng dn ngi nhn ngng ng k. iu ny cng cho ngi gi bit rng a ch email ca bn ang c s dng v bn c th s nhn c nhiu spam hn.

Hy s dng hai a ch email khc nhau, mt a ch s dng cho cc vic ring nh bn b, cng vic. Mt a ch s dng ng k tr thnh thnh vin ca cc din n, cc t chc... nhng ni m a ch email ca bn c th b lm dng hoc bn.

Khng nn ng a ch email ca bn nhng ni cng cng (v d nh cc din n, bng tin, chat room...) ni cc spammer thng s dng cc tin ch thu thp v tm kim a ch email.

S dng cc dch v email cung cp cng c chng spam, v d nh Yahoo! Mail, Gmail.

Khng bao gi c chuyn tip spam cho ngi khc.

Chuyn spam nhn c n ngi qun tr h thng email. Qun tr vin s thay i chng trnh lc ln sau h thng s chn li nhng email tng t nh th.