Tag Archives: Skype

Microsoft Researching Skype Password Reset Security Hole

This morning The Next Web reported on an exploit where Skype’s password reset web page could be used to hijack a user’s Skype account using only the password associated with the account. So… if you could guess someone’s email address (which can often be found through a Google search), you could effectively take over their Skype account.

Microsoft/Skype has DISABLED this feature while they investigate further so it appears that for the moment the security risk is limited.

However, it may be wise to watch closely the email account associated with your Skype ID for the next bit to see if any random password reset messages are sent to your account. Odds are that attackers will be sniffing around trying to see if there is any other way to exploit the apparent vulnerability.

The Next Web team reports that they were able to reproduce the attack on two Skype accounts of willing victims, confirming that the vulnerability was indeed real. They also reported the issue to Skype and worked with folks there.

The vulnerability is interesting in that it shows the complexity of modern communication applications. Skype is for the most part a desktop/mobile application, but yet it does rely on a centralized cloud-based service for authentication/passwords, etc. A vulnerability in the web interface for that central service then weakens the security of the overall system.

The “good” news for Microsoft/Skype is that because this appears to be a vulnerability in the web interface of the centralized system, this is probably something relatively easy for them to fix – and without requiring any client updates.

Kudos to Microsoft/Skype for reacting quickly to minimize the risk and we look forward to the issue being addressed.

UPDATE #1: Skype has issued a brief statement on their “heartbeat” web site with the same text that has been quoted in several articles.

UPDATE #2: The Verge has an article out now where many people in the comments are suggesting you change the email address associated with your Skype account to something less likely to be guessed. While Microsoft seems to have removed the immediate attack vector and this change is no longer critical to do, it may be something some of you may want to consider.

UPDATE #3: There’s a long Hacker News thread on this issue that also includes a link to an article walking through the exploit step-by-step as well as walking through links to protect your account. Note that because of the steps Microsoft has taken the exploit steps no longer work.

Skype for iOS/iPhone Vulnerable to Cross-Site-Scripting (XSS) Attack

News from the SUPEREVR security blog is that Skype for iOS is vulnerable to a cross-site scripting (XSS) attack that allows an attacker to send someone a message and, for instance, capture that user’s address book from their iPhone.

The author of the article posted a video that demonstrates the attack:

He further states in a tweet that he notified Skype of the vulnerability on August 24th:

In case anyone is wondering, I disclosed the vulnerability to Skype on 8/24. I was told an update would be released early this month.

Skype has issued a statement through their PR firm:

We are working hard to fix this reported issue in our next planned release which we hope to roll out imminently. In the meantime, we always recommend people exercise caution in only accepting friend requests from people they know and practice common sense Internet security as always.

Skype’s mitigation recommendation is a good one as the default privacy setting is typically that you can only receive chat messages from people on your Contact list. Therefore, the attacker would have to be someone who you have authorized and added to your contact list.

Meanwhile, hopefully Skype will be out with their update soon.

P.S. Hat tip to Tom Keating for writing about this exploit as that was where I first learned of it.

Skype encryption partially cracked?

skypelogo.jpgThe big news circulating through the Internet right now related to Skype is that someone may have reverse-engineered part of Skype’s encryption. Two posts of note:

The comments on the TechCrunch article are particularly worth reading as a number of security-related folks have jumped into the debate – and the author of the reverse-engineered code has jumped in as well (or someone claiming to be him, anyway).

People have been trying to reverse-engineer Skype’s proprietary encryption algorithm’s for years… and there have been various presentations at conferences and much data out there. In this case now, a developer named Sean O’Neil has made code available that apparently will decrypt one layer of Skype’s encryption.

Now, the code does NOT give you access to actual Skype messages. O’Neil writes in the TechCrunch comments:

Decryption of the RC4 layer gives nothing other than the ability to check CRC-32 of the packets, mere detection of random-looking encrypted packets as Skype. Maybe some firewalls will be able to block it at last.

I interpret that to mean that this code could help differentiate Skype traffic from other network traffic. The value there is really only, as the author says, that tools could be able to block Skype traffic because it could be more easily identified.

O’Neil goes on to say he has reverse-engineered more of Skype’s protocols and will be laying it all out at the Chaos Communication Conference in Berlin in December. We’ll have to see what gets said then…