Skype still down - Published DoS exploit may be culprit

Skype still down - Published DoS exploit may be culprit

Summary: [UPDATE 8/18/2007 - Another Russian site is claiming this was a DoS attack against Skype's authentication servers.  Skype continue to deny.

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[UPDATE 8/18/2007 - Another Russian site is claiming this was a DoS attack against Skype's authentication servers.  Skype continue to deny.] 

It's been a day and Skype is still down for me.  The task tray Skype logo never turns green for me and it keeps trying to connect.  The service was intermittently up on Thursday afternoon Pacific Standard Time but it hard down now.

Valery Marchuk of SecurityLab.ru may have an explanation for this world wide outage for Skype.  Marchuk posted the following message on the full disclosure mailing list:

Valery Marchuk: On SecurityLab.ru forum an exploit code was published by an anonymous user.  Reportedly it must have caused Skype massive disconnections today.

The PoC uses standard Skype client to call to a specific number. This call causes denial of service of current Skype server and forces Skype to reconnect to another server. The new server also "freezes" and so on ... the entire network.

Marchuk posted a link to the PoC (Proof of Concept) code for the exploit which I've left out.  If this is true, this sounds like the kind of low-cost non-brute force DoS (Denial of Service) attack that can bring down an entire service.  Since Skype is still down, this may be a very plausible explanation.

Skype is denying this is some kind of attack and posted the following note:

Hello everyone,

Apologies for the delay, but we can now update you on the Skype sign-on issue. As we continue to work hard at resolving the problem, we wanted to dispel some of the concerns that you may have. The Skype system has not crashed or been victim of a cyber attack. We love our customers too much to let that happen. This problem occurred because of a deficiency in an algorithm within Skype networking software. This controls the interaction between the user’s own Skype client and the rest of the Skype network.

Rest assured that everyone at Skype is working around the clock — from Tallinn to Luxembourg to San Jose — to resume normal service as quickly as possible.

Topics: Social Enterprise, Collaboration

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14 comments
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  • Not DOS according to Skype

    The following is a quote from the Skype website - use your own discretion
    Apologies for the delay, but we can now update you on the Skype sign-on issue. As we continue to work hard at resolving the problem, we wanted to dispel some of the concerns that you may have. The Skype system has not crashed or been victim of a cyber attack. We love our customers too much to let that happen. This problem occurred because of a deficiency in an algorithm within Skype networking software. This controls the interaction between the user?s own Skype client and the rest of the Skype network.
    tech_israel
    • Still looks down to me

      Still looks down to me and this isn't the first time they've had vulnerabilities.
      georgeou
      • Don't agree with "worldwide"...

        It seems to be working in Wisconsin without difficulty and has since yesterday afternoon.
        jasonp@...
        • Maybe in some countries...

          I just double-checked with my family and friends... and these are the confirmed location of them (with their skype all down):

          New York City, US
          Herts (Near London), UK
          Kuching, Malaysia
          Jakarta, Indonesia
          Melbourne, Australia

          Haven't checked with the others, but it seems to be quite serious.

          Cheers =)
          khopuki
  • "software problem"

    "software problem" could be just an euphemism for DoS exploit? or does the
    published exploit use anything else than software flaws?
    peter@...
    • Who knows, could be a euphemism indeed

      Who knows, could be a euphemism indeed. I STILL have problems getting in and it's been more than a day now.
      georgeou
  • Secure Because "We Love Our Customers"?

    Microsoft doesn't love you. Windows has been hacked before, and they talk badly about you behind your back at parties.

    Linux vendors don't love you. Linux has been hacked before, and they never remember your birthday.

    Apple doesn't love you. OS X has been hacked before, and they just sent you a cheap card for Valentines Day.

    America Online, Yahoo and Google? None of them love you, either. All hacked, because they just don't care about you.

    Only Skype is secure, and impervious to hacking and attacks. And that's because only Skype loves you.

    Skype: Because Everyone Else Hates You.
    Whyaylooh
    • AHAHAHAHAHAAHA, lol

      That was really funny.
      georgeou
  • This is real world IT, but

    what about things like troubleshooting? (The post about the NIC driver which corrupted certain packets, for instance. That would be really obscure to figure out if you weren't aware of the recent change.)

    What about good approaches to finding the source of some specific error based on your personal experience? Sharing experience and advice from running mail servers in general, how to aproach an unfamiliar network configuration (you're called into some business to install a new printer (need static IP address, no documentation exists)); what to be aware of. Good practise in general. I'm sure many fresh, as well as experienced IT consultants (among others) read this blog. I think I got my thougts across..

    PS: Sorry, I'll make this the last off-topic post.
    crashOverburn
  • http://www.ush.it/2007/08/18/why-the-skype-0day-exploit-is-a-fake/

    http://www.ush.it/2007/08/18/why-the-skype-0day-exploit-is-a-fake/
    fakefakefak3
  • back up

    from the website;



    Hello friends,

    Take a deep breath. Skype is back to normal.

    On Monday, we?ll provide a more detailed explanation of what happened. Until then, we?d like to apologize and thank you. Precisely in that order.

    We know how difficult and frustrating the past two days have been. And still, your good wishes kept flowing in. Thank you for the amazing patience, trust and support!

    UPDATED 18 August, 2007 11:00 GMT


    figured those reading the blogs would like to know it is back up, or so says their site. I can't confirm as i don't have Skype
    richvball44
  • "Skype Outage Caused by Microsoft Update"

    http://apnews.excite.com/article/20070820/D8R4R6HO1.html
    mlindl
  • I've had no problems with Skype

    At all. I wasn't online much on Tuesday or Wed of last week. Is that when it
    happened?

    I use Skype on a Mac. Does the Mac version use a different set of servers than
    Windows?
    mlindl
  • According to article on E-week.

    http://www.eweek.com/article2/0,1895,2173451,00.asp

    George, if you are going to continue in your bashing mode, at least get your facts straight before slandering those involved.
    bjbrock