Quarantine your infected users spreading malware

Gadi Evron ge at linuxbox.org
Mon Feb 20 21:40:48 UTC 2006

Many ISP's who do care about issues such as worms, infected users 
"spreading the love", etc. simply do not have the man-power to handle 
all their infected users' population.

It is becoming more and more obvious that the answer may not be at the 
ISP's doorstep, but the ISP's are indeed a critical part of the 
solution. What their eventual role in user safety will be I can only 
guess, but it is clear (to me) that this subject is going to become a 
lot "hotter" in coming years.

Aunty Jane (like Dr. Alan Solomon (drsolly) likes to call your average 
user) is your biggest risk to the Internet today, and how to fix the 
user non of us have a good idea quite yet. Especially since it's not 
quite one as I put in an Heinlein quote below.

Some who are user/broadband ISP's (not say, tier-1 and tier-2's who 
would be against it: "don't be the Internet's Firewall") are blocking 
ports such as 139 and 445 for a long time now, successfully preventing 
many of their users from becoming infected. This is also an excellent 
first step for responding to relevant outbreaks and halting their progress.

Philosophy aside, it works. It stops infections. Period.

Back to the philosophy, there are some other solutions as well. Plus, 
should this even be done?

One of them has been around for a while, but just now begins to mature: 
Quarantining your users.

Infected users quarantine may sound a bit harsh, but consider; if a user 
is indeed infected and does "spread the joy" on your network as well as 
others', and you could simply firewall him (or her) out of the world 
(VLAN, other solutions which may be far better) letting him (or her) go 
only to a web page explaining the problem to them, it's pretty nifty.

As many of us know, handling such users on tech support is not very 
cost-effective to ISP's, as if a user makes a call the ISP already 
losses money on that user. Than again, paying abuse desk personnel just 
so that they can disconnect your users is losing money too.

Which one would you prefer?

Jose (Nazario) points to many interesting papers on the subject on his 
blog: http://www.wormblog.com/papers/

Is it the ISP's place to do this? Should the ISP do this? Does the ISP 
have a right to do this?

If the ISP is nice enough to do it, and users know the ISP might. Why not?

This (as well as port blocking) is more true for organizations other 
than ISP's, but if they are indeed user/broadband ISP's, I see this as 
both the effective and the ethical thing to do if the users are notified 
this might happen when they sign their contracts. Then all the "don't be 
the Internet's firewall" debate goes away.

I respect the "don't be the Internet's firewall issue", not only for the 
sake of the cause but also because friends such as Steven Bellovin and 
other believe in them a lot more strongly than I do. Bigger issues such 
as the safety of the Internet exist now. That doesn't mean user rights 
are to be ignored, but certainly so shouldn't ours, especially if these 
are mostly unaffected?

I believe both are good and necessary solutions, but every organization 
needs to choose what is best for it, rather than follow some 
pre-determined blueprint. What's good for one may be horrible for another.

"You don't approve? Well too bad, we're in this for the species boys and 
girls. It's simple numbers, they have more and every day I have to make 
decisions that send hundreds of people, like you, to their deaths." -- 
Carl Jenkins, Starship Trooper, the movie.
I don't think the second part of the quote is quite right (to say the 
least), but I felt bad leaving it out, it's Heinlein after all... anyone 
who claims he is a fascist though will have to deal with me. :)
This isn't only about users, it's about the bad guys and how they 
out-number us, too. They have far better cooperation to boot.

There are several such products around and they have been discussed here 
on NANOG before, but I haven't tried them myself as of yet, so I can't 
really recommend any of them. Can you?

I'll update on these as I find out more on: http://blogs.securiteam.com

This write-up can be found here: 



"Out of the box is where I live".
	-- Cara "Starbuck" Thrace, Battlestar Galactica.

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