[nSLUG] Re: Security on dialup

Mike Spencer mspencer at tallships.ca
Thu Feb 27 04:01:17 AST 2014

On 02/26/2014 02:56 AM, Mike Spencer wrote:
> If I had an always-on high speed internet connection, there are
> several things I'd have to change, I guess.  As it is, one box is
> episodically on the net by dial-up.

To which Ben replied:

ben> It's a game of percentages, isn't it? Always-on high speed
ben> internet means more time for the attacker to attack you, but how
ben> long, exactly, do you think it takes for an attack to succeed?

Well, roughly, at least 100 times longer for me than for you. :-)

The few attacks I've read about in detail involve a small piece of
compromising code that then fetches a much larger chunk of code.  With
blinkenlights on my desk and 38K bps, "much larger" is (would be)
at least potentially noticeable. 

I do run iptables(8) on my dial-up box. For high-speed, always-on, I
probably should do a more sophisticated job of configuring it. In the
last hour, I've seen SYN probes from China on ports 25, 22, 23, 80 and
8088 and one on port 22 from India that were successfully
ignored. ("Seen" because I often leave tcpdump running in a window
that peeks out from behind other windows, where unexpected scrolling
of data gets my attention better than the modem lights.)

I also run a script in the background that checks several critical
system files every few minutes and plays a loud audible alarm if one
of them changes.  It goes off every afternoon when cron does log rotate.

Although fans of fancy interactive sites would see it as a sort of
sacrifice, I rarely do anything that involves js or Java and don't
auto-run any code. Attachments in email are manually unpacked.

ben> I think an admin on a system connected via dialup should be every
ben> bit as careful about security as one on high speed Internet.

Yes, of course.  I think the threat is lower. I'm probably more
concerned about mass surveillance than intrusion. (Email packets to my
wife, who is physically in the next room, go through the US and are
subject to collection & scrutiny as "foreign" communication.)

And, back to the original critique, I don't see how telnet between
local boxen through a router that is not itself on the net is a
potential risk. Perhaps I should.

- Mike

Michael Spencer                  Nova Scotia, Canada       .~. 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

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