????????????????????????CentOS ???????????ü????????? ??????????DigitalOcean??CentOS 6 VPS????????????????????????????????????????LINUX???? ?????????и????????????????????VPS??????÷????????????
??????????????? ??????漰?????????????????????????Щ?????????????????????????????????????
??????????????? ??? ???????????? ??????????????????????衣
?????????????????????iptables????????????google????????????????????!
????????????????????IPTables:
????iptables??Linux???????????????????????????????????table?? chain??????????????????????????NAT?? ?????????iptables??????????????CentOS 6??????Linux?汾?У?????iptables????????????????  iptables?????IPv4?? ??????IPv6????????ip6tables.
????iptables??????????
????iptables [-t table] command [chain] [rules] [-j target]
????[-t table] ??????????????? ?????????: filter?? nat ?? mangle?????δ??????????filter???????? ?????????????????????????????????????????????????filter????????OK???filter????? INPUT?? OUTPUT????FORWARD????chain.
????command ????iptables???????????????
????-A ??–append): ???????????????????chain???β??
????-D??–delete)??????????????
????-F ??–flush) ????????chain?? ?????chain?е????й??????δ???chain?? ?????????chain?е????й???
????target: ?????????????????? ???????漸???
????ACCEPT: ?????????(???????????????????????????chain.
????DROP??  ?????
??????????REJECT?? RETURN?? LOG?? REDIRECT?? MARK?? MIRROR?? MAQUERADE???
?????????iptables????????????????????? iptables man page ?????? .
???????????iptables????????????е????(rule)????  ???????????????? ?????κ???Щ??????б?????????÷?????????壬?????????????????????ACCEPT?????????DRIP????????????κι??????壬????????????á?
???????????????
?????????????????DigitalOcean/ Linode/ ????????????????????????? ?? ????????? iptables?????ó??????????п??????????????????????????????????????????? ?????????????????????????????????????????????и?????????? DigitalOcean???????web console????棬???????????????iptables??????????????????У?
??????????Щ??????????
????????? SSH ????22?????????????????????????????????????
?????????????CentOS??VPS?????????LAMP????Web????????FTP???????? Mail?????????
????????Web????????????????80?????????HTTPS/SSLЭ???????????????443???
????????Mail??????????????漰SMTP?? POP3?? IMAPЭ?飬?????????????￡?
????SMTP : 25   Secure SMTP:465  POP3: 110   Secure POP3: 995   IMAP: 143   IMAP over SSL: 993
????????FTP???????????????? 20?? 21???????
??????????? ???γ????????
??????????￡?CentOS??iptables?????????????κ???????????