??????? Outbound Port 25 Blocking(OP25B)?????? ADSL

1
???????Outbound Port 25 Blocking(OP25B)??????ADS
L B????????????

• 2006?8?
• ??????????????
• ????????
• ?????????

2
????
??????????????????????? ????????????????????????
?????????????????????????????????????????????????
?????????????????????????????????????????????????
??????????????????????????????
?????????????????????????????????????????JEAG?1(Ja
pan E-mail Anti-Abuse Group) ????????Recommendatio
n????Outbound Port 25 Blocking(??OP25B)??????????
??? ??????????????????????FreeBit,Vectant?OP25B
?????????????????????????????????????????????? ?
1 JEAGJapan E-mail Anti-Abuse Group ????????????
????????????????????????????????????????????? ???
??????????????
3
1.OP25B????????

• ?Outbound Port 25 Blocking(OP25B)????????????????
  ???????????????(Port??)?????????????(SMTP)????????
  25?(Port25)????Block??????????????????????????????
  ???PC?????????????????????????????????????????????
  ???????
• ?????????????
• NTT?????????????????????
• ??(??)IP?????????? ??IP??????????????
• ????
• STEP1 ???????OP25B???
• STEP2 ??(??)IP??????????????OP25B???
• ???????????

4
2.?STEP????

• STEP1???????OP25B???
• ?????????????????????????????????????????????????
  ??(??)????????????????????????????????????????????
  ????????????
• ????????(??)IP?????????????????????????????????
  ??????OP25B???????????????
• STEP2 ??(??)IP??????????????OP25B???
• ?????????????????(??)IP??????????????????????????
  ???????PC???(??)IP????????????????????????????????
  ?????????????????
• ????????(??)IP????????????????????OP25B?????????
  ????????
• ???STEP2?????????????????????4??????????
• ??????Submission Port SMTP AUTH????????????

5
3.??????(??)
2006/08 2006/09 2006/10
2006/11 2006/12 2008/01
?????????

???????OP25B????

??????OP25B??
?????????????????
??????

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4.?????(Submission Port SMTP AUTH??)

• 2007?12???????
• ?Submission Port (TCP Port587)SMTP
  AUTH?(??587??)?????????????
• ??????
• ?????????????????????? SMTP ???(TCP
  Port25)????????????????587???????????????????????
  ???
• ???????????????????????????(???2?)????????
• a. ?????????????????? 25 ? 587 ?????
• b. ???????????????????????
• ???????????????
• ??(??)IP?????????????????DNS???????????????????
  ??
• ???IP??????????????????????????
• ????????????????????????????????????

7
STEP1???????OP25B???

8
STEP3??(??)IP?????????????? OP25B???

Port25
??
Port587
Port25
??IP??????
?ISP ?????????
Port25
Port25
??
Port587
????????? ?????????
Port25
?????
????? ?????????
Port25
??(??)IP??????
????????
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??.OP25B ???????
A?ISP
B?ASP
MailServer A
MailServer B
???????
Server?? 587Auth?????
Client?Server??? 587Auth????
C?ISP
Vectant/?????????
MailServer C
Client?Server??? 587Auth?????
?????
Port25?????????????
Flets
Flets
Port587 Auth??
Port25 Blocking
Flets
Port25?? (????)
Port25??
? ?????????????????? ?????????????????????