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Tcp

Friday, October 03, 2008

Why The TCP Attack Is Likely Bad, But Not That Bad

By Rich

There’s been a bunch of new information coming out the past few days about the potential big TCP denial of service flaw. The three most informative posts I’ve read are:

  1. Fyodor’s discussion of either the same, or a similar issue.
  2. Richard Bejtlich’s overview.
  3. Rob Graham’s take on the potential attack.

Here’s what I think you need to know:

  1. It is almost certainly real.
  2. Using this technique, and attacker with very few resources can lock up the TCP stack of the target system, potentially draining other resources, and maybe even forcing a reboot (which could trash the host OS).
  3. Anything that accepts TCP connections is vulnerable. I believe that means passive sniffing/routing is safe.
  4. The attack is obvious and traceable. Since we are using TCP and creating open connections (not UDP) it means spoofing/anonymous attacks don’t seem possible.
  5. Thus, I’d be more worried about a botnet that floods your upstream provider than this targeted attack.
  6. This is the kind of thing we should be able to filter, once our defenses are updated.

In other words- a bad attack, but a moderate risk. That said, there are aspects of this that still concern me and we need to keep in mind:

  1. We don’t know if our assumptions are correct. This could be a different, and much more serious, technique. Such as something spoofable. Unlikely, but possible.
  2. Nothing says a botnet can’t use this- and thus make filtering and tracing a real pain. Imagine a botnet rotating this attack technique around to different nodes. It could support more efficient botnet attacks, that could then drop to regular flood mode if it doesn’t think the more efficient direct mode is working.
  3. We don’t know it doesn’t do something to the router infrastructure or passive monitoring. Again, unlikely based on the information released, but I’d hate to dismiss this as concerning until we know more.
  4. Until there’s some sort of fix, the Defcon network and coffee shops near universities are really going to suck.
  5. Until this is fixed, small businesses and individuals are the most likely to suffer. An enterprise might be able to detect and drop an attack like this, but individual users and small business don’t have the resources. Get ready for vendor pouncing.

–Rich

Friday Summary

By Adrian Lane

The Securosis team is attempting to regroup and prepare for a busy Q4. It took three full days, but I am fully migrated into the Mac Universe and engaged in a couple of research projects. Now productive, I can finally start work on a couple research projects. Rich has left HQ in search of coffee, quiet and a security muse while he catches up on writing projects and white papers. But even though we have a short term ban on travel and conferences, there is a lot to talk about. Here is our summary of this weeks blogs, news and events.

Webcasts, Podcasts, and Conferences:

Favorite Securosis Posts:

  • Rich: Impact of the Economic Crisis on Security. It doesn’t matter if you are a vendor or practitioner, we’ll feel the effects of this crisis, but in a predictable way.
  • Adrian: Email Security. It’s getting cheaper, faster and easier to implement, but with some potential privacy issues depending on how you go about it.

Favorite Outside Posts:

  • Adrian: Brian Krebs post on lawsuits against ‘Scareware Purveyors’. Finally. Infecting someone’s machine with spyware and using it as a marketing and sales conduit is akin to stealing in my book. Now if they would only go after the purveyors of this scare tactic.
  • Rich: Fyodor explains (probably) the looming TCP attack. Fyodor, creator of NMAP, does an excellent job of explaining how the big TCP DoS attack likely works.

Top News:

  • The recovery bill. Law makers look panicked, and the market goes down every time they get close to a ‘solution’.
  • The TCP Denial of Service attack. Nothing to panic about, and we’ll write more on it, but very interesting.

Blog Comment of the Week:

Chris Pepper’s comment on Rich’s “Statistical Distractions” post:

[snip]... I refuse to use unencrypted email, but that”s to the SMTP/IMAP/POP/webmail server. But for email we have to keep in mind that the second hop – to the destination SMTP server – is almost always plaintext (unencrypted SMTP). So it’s more about protecting the account credentials than about protecting the email itself, but someone gaining full access to my whole multi-gigabyte mail store would really really suck. …[/snip]

Now, I am off to The Office for the Securosis weekly staff meeting. We hope you all have a great weekend.

–Adrian Lane