[arm-allstar] Firewall thoughts ---was:Trouble with Supermon

[John Huggins]

Very true, but the attacks, though failure they will certainly be with
key auth, still drain resources from your system in the mere attempts.

John

On Wed, May 16, 2018 at 9:34 PM, "Jeff Karpinski via arm-allstar"
<arm-allstar at hamvoip.org> wrote:
> Really should disable password SSH logins. Limit to pre-shared keys and it won’t matter what bit what port you use. 22 is fine.
>
>
>> On May 16, 2018, at 7:18 PM, David McGough via arm-allstar <arm-allstar at hamvoip.org> wrote:
>>
>>
>> Hi Guys,
>>
>> I haven't commented much about the firewall / open ports issue, so
>> far...I've been really busy this week.
>>
>> Anyhow, I agree with Tony that "security by obscurity" is indeed a viable
>> strategy to reduce the number of drive-by port scans and attacks. But, the
>> ports you choose must truly be OBSCURE! For example, with a SSH server,
>> ports 22, 222, 2022, 2222, 4022, etc., (most everything ending in "22")
>> will get rampantly scanned!!  But, put ssh on port 7589. Nada! Not a
>> single scan!
>>
>> There are a number of excellent tools for Linux which will help with
>> understanding what ports are open and the traffic on your network, too.
>> Some are: netstat, nmap and tcpdump/wireshark.
>>
>> Running a "netstat -anp" (as root) on your local Linux box show all the
>> current network bindings, including open ports, connections to ports, etc.
>>
>> The nmap program is a "hackers wonderland" ...nmap is a robust tool which
>> will allow you to actively probe networks looking for open ports, hidden
>> devices, etc. Just do BE AWARE that if you probe someone's network on the
>> Internet, you'll likely trip intrusion alarms!!! This type of Internet
>> probing is also a violation of most ISP's acceptable use policies--so be
>> careful with this tool!!!!
>>
>> tcpdump and wireshark/tshark help round out your network analysis toolkit!
>> These tools allow you to "sniff" all the traffic passing through a network
>> interface by placing the interface in promiscuous mode---meaning it
>> reports anything it can hear, whether destined for its IP address or not.
>> I won't get into the details about these scanners in this message or I'll
>> be writing a novel--these tools are VERY sophisticated! For example, you
>> can use them to sniff plain-text passwords or even passively monitor and
>> PLAY the actual audio traffic from Asterisk/AllStar!
>>
>>
>> Finally, I want to mention that firewalls are not the end-all be-all of
>> security and they can lull you into a FALSE sense of security! Here is an
>> example of how this is frequently true: Lets say that your system has 3
>> ports open: port tcp/222 (ssh), port tcp/80 (http) and port udp/4569
>> (IAX2). You setup a firewall and block everything, but open pinholes for
>> the 3 ports listed above. Your firewall allows everyone to connect to
>> these ports, no restrictions....So, what have you accomplished with the
>> firewall????  NOTHING!  ....I'll end on this note as something to ponder.
>>
>>
>> 73, David KB4FXC
>>
>>
>>
>>
>>
>>
>> On Wed, 16 May 2018, "Tony Ross via arm-allstar" wrote:
>>
>>> While some people would criticize such alternate ports for wks
>> (well-known services) as "security by obscurity", it does work.
>>
>> I had a repeater owner ask for my help, as one of his irlp nodes seemed
>> to not respond to ssh client requests; he couldn't log in remotely. It
>> was difficult, but I eventually found a prompt. I immediately looked at
>> /var/log/* and found some very large syslog files. Looking at their
>> contents showed an ssh attack on port 22, so I changed the port to
>> something in a different range, re-started the sshd and the problem stopped.
>>
>> Using simple system tools such as grep, sort, awk, uniq and wc, it was
>> easy to find that > 3.7 million ssh attempts in 4 days from 4 east-Asian
>> IP addresses had essentially crippled the system.
>>
>> It did speak well for his choice of passwords though.
>>
>> On 05/15/2018 07:19 PM, "Charles Powell via arm-allstar" wrote:
>>> I use a port in the 9000s because it is an unexpected service there.  Your mileage may vary.
>>>
>>> 73,
>>>
>>> Charles - NK8O
>>>
>>>> On May 15, 2018, at 12:59 PM, Doug Crompton via arm-allstar <arm-allstar at hamvoip.org> wrote:
>>>>
>>>> Typically port 8080 is used but you can use high number if that does not
>>>> work. Here are three examples - 15700, 16300, 17400  but you are not
>>>> limited to them.
>>>>
>>>>
>>>> *73 Doug*
>>>>
>>>> *WA3DSP*
>>>>
>>>> *http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*
>>>>
>>>>
>>>>
>>
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