LinuxQuestions.org - firewall question

- Linux - Networking (https://www.linuxquestions.org/questions/linux-networking-3/)

- - firewall question (https://www.linuxquestions.org/questions/linux-networking-3/firewall-question-350329/)

firewall question

on windows xp , if you have installed a firewall such as kerio , norton (others) if a new software attempts to connect to internet the firewall tell you on which port is trying to connect . With linux is there some software which could advice me in a similar way ?

thank you

You can see which connections are being made to your machine with:
netstat -an

To log the requests that are made and blocked add a logging rule to your iptables rule set.

Quote:

To log the requests that are made and blocked add a logging rule to your iptables rule set.

this could be very useful for me ! Can you tell me how to that ?

Thank you!

The iptables man page has the details:

Code:

  LOG

      Turn on kernel logging of matching packets.  When this  option  is  set

      for  a rule, the Linux kernel will print some information on all match-

      ing packets (like most IP header fields) via the kernel log  (where  it

      can be read with dmesg or syslogd(8)).  This is a "non-terminating tar-

      get", i.e. rule traversal continues at the next rule.  So if  you  want

      to  LOG  the  packets  you refuse, use two separate rules with the same

      matching criteria, first using target LOG then DROP (or REJECT).



      --log-level level

              Level of logging (numeric or see syslog.conf(5)).



      --log-prefix prefix

              Prefix log messages with the specified prefix; up to 29  letters

              long, and useful for distinguishing messages in the logs.



      --log-tcp-sequence

              Log  TCP sequence numbers. This is a security risk if the log is

              readable by users.



      --log-tcp-options

              Log options from the TCP packet header.



      --log-ip-options

              Log options from the IP packet header.



      --log-uid

              Log the userid of the process which generated the packet.