{"id":261,"date":"2012-02-07T00:23:14","date_gmt":"2012-02-07T05:23:14","guid":{"rendered":"http:\/\/josephpcohen.com\/w\/?p=261"},"modified":"2015-03-27T11:53:18","modified_gmt":"2015-03-27T15:53:18","slug":"iptables-introduction-and-overview","status":"publish","type":"post","link":"https:\/\/josephpcohen.com\/w\/iptables-introduction-and-overview\/","title":{"rendered":"IPTables : Introduction and Overview"},"content":{"rendered":"

\n\"pdf\"
\nDownload the lecture here<\/a>
\n\"pdf\"
\nWatch the lecture here<\/a><\/div>\n

<\/p>\n

Here is some text from the slides:<\/p>\n

+ what is iptables?
\niptables is the userspace command line program used to configure the linux packet filtering ruleset
\n + a.k.a. firewall<\/p>\n

what?
\na packet filter is a piece of software that looks at the headers of packets as they pass through, and decides the fate of the entire packet
\nwhy?
\n+ control
\n allow only what you specify
\n+ security
\n protect against evil >:|
\n+ watchfulness
\n alerts of abnormal activity<\/p>\n

traffic can be characterized by:
\n+ source and\/or destination ip
\n trust certain hosts
\n+ source and\/or destination port
\n allow specific services
\n+ protocol type
\n tcp, udp, icmp, etc…
\n+ additional parameters
\n e.g. state, <\/p>\n

+ review: ports
\nOnce a packet has reached its destination host, it is sent to a specific port.
\n+ about 65,000 available ports per host
\n+ the first 1024 are reserved to privileged
\n processes such as daemons
\n+ \/etc\/services defines well-known ports
\n e.g. Telnet:23, FTP:21, HTTP:80<\/p>\n

+ review: protocols
\nRepresent the kind of traffic being sent.
\n+ tcp \/\/ transmission control protocol
\n maintains a connection between two hosts
\n+ udp \/\/ user datagram protocol
\n sends data statelessly, without
\n establishing a connection
\n+ icmp \/\/ internet control message protocol
\n administrative functions such as PING<\/p>\n

+ basic operations
\n-L List the rules.
\n-I Insert a new rule before .
\n-A Append a new rule at end of chain.
\n-R Replace rule with new rule.
\n-D Delete rule .
\n-F Flush the chain (delete all rules).
\n-X Delete the chain
\n-P <\/p>\n

Set <\/p>\n

as default policy for chain.
\n-t <\/p>\n Specify table. default is
\nfilter
\n-j Jump to chain target<\/p>\n","protected":false},"excerpt":{"rendered":"

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