Re: Other Open Ports

[Mike McClain <mike.junk@nethere.com>]

Howdy,
On Mon, Jul 23, 2012 at 01:21:55PM -0500, Charles Kroeger wrote:
> I'm thinking my firewall 'Shorewall' encompasses an extensive enough design to
> cover any attempts of intrusion that may occur, I do notice notwithstanding, that
> although ports 0 and 1 are closed, they still show up on test like grc.com's
> 'shields-up' port scanner.
> 
> I know that 0 <nil> is not a port and yet it is a port as 0 is a number in our
> world and port 1 has its function described, so why would these two ports
> even show up?
> 
> On Debian it seems whatever firewall one uses these two ports are always visible
> and closed, so if port 0 is not a port and and port 1 is always closed, why do they
> announce themselves if pinged?
<snip> 

I've been using Shorewall in Debian since Woody and always passed 
GRC's 'shields-up' port scanner full stealthed.

Try these that I set from some hardening doc I read somewhere.

root@/deb40a:~> ed /etc/sysctl.conf
    # Ignore ICMP ping
    net/ipv4/icmp_echo_ignore_all = 1

net/ipv4/icmp_echo_ignore_broadcasts = 1
net/ipv4/icmp_ignore_bogus_error_responses = 1

G'luck,
Mike
-- 
Satisfied user of Linux since 1997.
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