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Special Forums IP Networking Question about blocking incomming traffic Post 302859773 by LMHmedchem on Thursday 3rd of October 2013 07:34:50 PM
Old 10-03-2013
Question about blocking incomming traffic

Hello,

Like many others, I have continued to get attempts to connect to my local net router from the Asia Pacific Network Information Centre and from RIPE Network Coordination Centre, Amsterdam. I would say that 90% of attempted connections come from these two locations. The originating IP address is usually not registered in ARIN, so there is no specific IP range I can block. It is probably pointless to block individual IP addresses, so I have been thinking about other methods.

I began wondering why I should allow any inbound connections, meaning connection requests that originate off of my local net. After thinking about this, I realize that I don't fully understand these protocols as well as I should. Can someone explain whether or not I should block all incoming connections (I am not running any kind of service that would need incoming connections, ftp, sshd, etc). If I can't block all of them, which ones should I continue to allow? What would such a firewall rule look like, etc?

Thanks for any assistance that you can provide.

LMHmedchem
 

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TCPDROP(8)						    BSD System Manager's Manual 						TCPDROP(8)

NAME
tcpdrop -- drop TCP connections SYNOPSIS
tcpdrop local-address local-port foreign-address foreign-port tcpdrop [-l] -a DESCRIPTION
The tcpdrop command may be used to drop TCP connections from the command line. If -a is specified then tcpdrop will attempt to drop all active connections. The -l flag may be given to list the tcpdrop invocation to drop all active connections one at a time. If -a is not specified then only the connection between the given local address local-address, port local-port, and the foreign address foreign-address, port foreign-port, will be dropped. Addresses and ports may be specified by name or numeric value. Both IPv4 and IPv6 address formats are supported. The addresses and ports may be separated by periods or colons instead of spaces. EXIT STATUS
The tcpdrop utility exits 0 on success, and >0 if an error occurs. EXAMPLES
If a connection to httpd(8) is causing congestion on a network link, one can drop the TCP session in charge: # sockstat -c | grep httpd www httpd 16525 3 tcp4 192.168.5.41:80 192.168.5.1:26747 The following command will drop the connection: # tcpdrop 192.168.5.41 80 192.168.5.1 26747 The following command will drop all connections but those to or from port 22, the port used by sshd(8): # tcpdrop -l -a | grep -vw 22 | sh SEE ALSO
netstat(1), sockstat(1) AUTHORS
Markus Friedl <markus@openbsd.org> Juli Mallett <jmallett@FreeBSD.org> BSD
January 30, 2013 BSD
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