Re: Wifi Security

["Steven M. Bellovin" <smb () cs columbia edu>]

In message <Pine.LNX.4.64.0511211400000.12605 () twin uoregon edu>, Joel Jaeggli w
rites:
> On Mon, 21 Nov 2005, Stephen J. Wilcox wrote:
>
> <snip>
> > > What do you learn by looking at someone's ipsec, ssl-wrappered, or ssh
> > > tunneled traffic?
> >
> > no, we're not trying to do that, you dont really think that because its
> > encrypted it cant be decrypted do you?
>
> I do believe (reasonably so, I think) that if I'm going have a 
> conversation with a second party whom I already trust, that a third party 
> will have trouble inserting themself into the path of that conversation 
> without revealing their presence..
>
> <snip>
>
> > you dont have to break the code if the endpoints trust sessions with you and
> > share their encryption keys
>
> Successfully inserting yourself in the middle requires some 
> social-engineering or really bad protocol design. The former can be 
> mitigated through vigilance, the later falls into the realm of peer review 
> and security research.

The problem is "vigilance", especially as applied to non-security aware 
users.  Here's a quick test: pick a bunch of smart, non-geek computer 
users and ask them what a certificate is and what a certificate 
authority is.  Then inquire what they'd do when the web page they were 
looking at had some text similar to what I posted yesterday.

You're absolutely right that sufficient vigilance -- coupled with good 
user interfaces -- should be adequate.  Note my qualifiers: 
"sufficient", "good", "should be".  Demonstrably, they're not.  (A few 
years ago, a company I know of deployed a browser+Java-based expense
voucher application.  The login screen said "when you're asked if this 
applet should have extra permissions, just click yes, even though the 
pop-up warns that that could be dangerous".  A security-clueful person 
I know complained about the bad habits this was instilling.  The answer 
he got back was "we've checked it out; this application really is ok".
Talk about unclear on the concept...

That said, ssh (which you cited in another post) does a better job.  It 
gives a very big warning that stresses the danger.  By contrast, 
Firefox (and I think IE, though I'd have to find a Windows machine to 
test that) tells you that various forms of certificate problems are 
unlikely.  The big thing ssh does is that it keeps a history -- it 
binds the warning to your previous history.  That's a much better 
strategy than relying on ~80 CAs you've never heard of.
> If I may paraphrase the original posters question (Ross Hosman), it was:
>
> Do large wireless buildouts present a new security threat due to the 
> potential to spoof AP's?
>
> The answer to that is no, this is a threat we live with currently. We have 
> tools to mitigate the risks associated with it.
>
> You can say that consumers are stupid, and won't figure this out, and that 
> may be true; however when it's starts to cost them losts money, they will 
> sit-up take notice and buy tools to solve this problem for them, just like 
> they do with any other security threat that goes beyond being an anoyance. 
> probably said product will be blue, say linksys on it, and have the word 
> vpn (among others) buried on the packaging someplace.

Given reports I've seen about public terminal usage, I'm much more 
skeptical.  See, for example, http://www.theregister.co.uk/2005/09/21/airport_pc_security_lax/
I frequently take the train to Washington; I've occasionally noticed 
other PCs that appear to be looking for an access point.  I've been 
tempted to put my machine into host AP mode (or use my travel access 
point -- these trains generally have AC power), run a dhcp server, and 
see what passwords I get.  But I've never been able to convince myself 
that it would be legal, let alone ethical.

                --Steven M. Bellovin, http://www.cs.columbia.edu/~smb