2 Asterisk Security Vulnerabilities Could Lead To Remote Crashes

Asterisk logoThe great folks on Digium’s security team published two security advisories this week that could lead to remote crashes of an Asterisk server.

The first, AST-2013-004, Remote Crash From Late Arriving SIP ACK With SDP, has this description:

A remotely exploitable crash vulnerability exists in the SIP channel driver if an ACK with SDP is received after the channel has been terminated. The handling code incorrectly assumes that the channel will always be present.

The second, AST-2013-005, Remote Crash when Invalid SDP is sent in SIP Request, has this description:

A remotely exploitable crash vulnerability exists in the SIP channel driver if an invalid SDP is sent in a SIP request that defines media descriptions before connection information. The handling code incorrectly attempts to reference the socket address information even though that information has not yet been set.

My one critique of the security advisories is that they don’t contain any “mitigating circumstances” that explain the circumstances under which the vulnerabilities could be exploited. For instance, it would seem from reading the documents that at least in the first case there would need to be a successful SIP connection established first – and then ended – before the packet could be received that would cause the crash. Unfortunately I don’t personally know Asterisk’s internals well enough to comment on that.

Regardless, the fix here is to upgrade to the latest versions of Asterisk as documented in the security advisories.

Kudos to the Digium folks for issuing these advisories and continuing their clear process of letting people know about security within Asterisk.

VoIP Security Major Topic This Week at SIPNOC 2013


sipnoc-2013This week the SIP Network Operators Conference (SIPNOC) takes place in Herndon, Virginia, and the SIPNOC agenda turns out to have a great focus on security as it relates to VoIP and IP-based communications in general.   The security-related sessions include:

  • The Growth of Robocalling SPIT
  • Communications Service Providers and Threat Intelligence Sharing
  • Panel Discussion: Anatomy of a VoIP DMZ
  • VoIP Theft: Werewolf or Hydra
  • Who are You Really Calling? How DNSSEC Can Help

There will also be a “VoIP Security Birds-of-a-feather (BOF)” session tomorrow evening where we’ll be sharing information about VoIP security issues and learning from each other about what issues people are seeing.

Sponsored by the SIP Forum, SIPNOC is an educational event that brings together primarily technical and operations staff from a wide range of telecommunications and VoIP service providers.  It is not a trade show, i.e. there is no exhibit hall.  It is just focused on providing educational sessions and networking opportunities.

I’ll be there at SIPNOC speaking about DNSSEC, IPv6 and moderating the VoIP security BOF and the VoIP DMZ panel . I look forward to meeting up again with many of the folks who have attended SIPNOC in the past years.   The event is not livestreamed, but if you are in the DC area and want to attend, registration is still open.

If you are there at SIPNOC 2013, please do say hello!

U.S. DHS Warns of TDoS (Telephony Denial of Service) Attacks

DHS TDOS AlertThe U.S. Department of Homeland Security recently issued a bulletin titled “TDoS Attacks on Public Safety Communications” and while it was “Law Enforcement Use Sensitive/For Official Use Only” a copy was obtained by Brian Krebs who wrote about it on his site and also published the DHS bulletin publicly.

This resulted in a small flurry of related articles that Mark Collier listed on his VoIP security blog. Most of the articles, unfortunately somewhat predictably, seem to be rehashes of Brian Krebs’ post and/or the DHS bulletin.  However, the point is definitely solid – these are real attacks that are happening on call centers out there, including those operated by emergency services organizations.  No one wants to be on the receiving end of hundreds (or thousands) of phone calls clogging up your call center and making it unusable for regular business.

The connection to VoIP is that made by Brian Krebs in his article:

According to a recent report from SecureLogix, a company that sells security services to call centers, free IP-PBX software such as Asterisk, as well as computer-based call generation tools and easy-to-access SIP services, are greatly lowering the barrier-to-entry for voice network attackers.

This is the key point.  VoIP systems make these kind of attacks much easier to create.  Anyone can take one of the various free VoIP servers and create a script that will generate a crazy number of phone calls.  And of course the Caller-ID can be easily spoofed using the same servers.  I’m sure there are already scripts out there that automate all of this for would-be attackers.

The challenge is then finding either a VoIP service provider (or “ITSP” or “SIP Service Provider”) who will let the attacker send out phone calls to the PSTN – or to find victims that allow incoming SIP connections (which means that attacks could come from any Internet connection).  Or to find components of the SIP signaling infrastructure that have weak (or no) authentication and through which an attacker can send calls.  For example, SIP gateways that allow incoming SIP calls with minimal (or easily spoofable) authentication.

It’s not necessarily easy to do, but VoIP systems do make it easier than it was in the past, largely because the attackers can obtain a degree of anonymity through masking their source, and also because of the automation of the calling possible through the systems.

Defending against a TDoS is not the easiest, particularly when the attackers can use spoofed Caller IDs to hide their origin.  Here is a place where VoIP actually helps because if the calls are coming in over IP, firewalls and other network monitoring tools can be used to recognize patterns and potentially identify and block sources of the attacks.  There are companies such as SecureLogix (whose CTO is Mark Collier, whom I linked to earlier) who do sell products and services to help address these threats. As we increasingly move to IP-based communications there will no doubt be many more companies and service providers offering such services.

We as an industry do need to do what we can to help people understand both the threat posed by these attacks, and also the mitigations and possible solutions.

In the meantime, expect more people to be talking about this issue due to this DHS bulletin and the surrounding attention in the media.

What do you think?  What should be done within the VoIP vendor/organization community?  What are good steps to promote to defend against TDoS attacks?

Is The “VoIP” in “VoIP Security” Still The Right Term?

VoipqShould we still be talking about “VoIP security”? Or should we be using some other language?

Back when we started VOIPSA in 2005, “voice over IP (VoIP)” was the term we all were using, but as we look at what kind of activities come next, we’re starting to wonder if we should be talking about “communications security” a bit differently.

For starters, in the past 8 years we’ve moved far beyond simply “voice” into video over IP, text messaging over IP, data sharing over IP… all within a single communications session. Is that still “VoIP”?

Beyond that, we’ve seen a range of other terms coming into usage, including:

  • unified communications (UC)
  • real-time communications (RTC)
  • cloud communications
  • IP communications

and many more. Plus new technologies are out that have pushed “VoIP” beyond its traditional proprietary protocols and the open standard of the Session Initiation Protocol (SIP). We’ve seen the strong emergence of XMPP (Jabber) and its related “Jingle” protocol. We’ve seen the explosion of interest in the WebRTC / RTCWEB protocols and tools.

Are all of those “VoIP”? Or are they something more?

Should we be talking about…

  • UC security?
  • real-time communications security?
  • IP communications security?

Or perhaps just plain old “communications security”? (or is that too generic?) I’ve seen some people talking about “SIP security”, but now that is specific to a single protocol.

Or is “VoIP security” still an okay term to use?

What do you think? What do you use? What do you hear vendors and others using? How should we be talking about securing all these many ways we have to communicate now over IP networks?

Please do let us know either as comments here or out on social networks. (Thanks!)

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.

Digium Releases 3 Asterisk Security Advisories

Asterisk logoThis week Digium released three security advisories allowing remote authenticated sessions to either crash an Asterisk server or escalate user privileges.  The advisories are:

In all cases the solution is to upgrade to the latest releases of Asterisk Open Source (1.6.2.24, 1.8.11.1 or  10.3.1 ) or Asterisk Business Edition (C.3.7.4).

 

Free Webinar Tomorrow: Securing VoIP and Unified Communications Systems

USTelecomWant to join in to a free webinar/webcast to learn about VoIP and Unified Communications security? Tomorrow, Thursday, January 26, 2012, I (Dan York) will be speaking as part of US Telecom’s monthly educational webinar series on the topic of: “Securing VoIP and Unified Communications Systems“

The session will be at 1:00pm US Eastern. Registration is free using the “Register Now” link on the right side of the US Telecom webinar page. I’ll be spending about 30 minutes covering the range of security issues with VoIP and UC and then will have plenty of time for questions.

The abstract of the session includes:

What are the major security threats to today’s telecommunications infrastructure?

As telecom has evolved from the traditional circuit-switched PSTN to a new world of Voice-over-IP (VoIP) and Unified Communications (UC), what are the security implications? As services move to be based on the Session Initiation Protocol (SIP), how does that change the security of the system? Is this new IP-based world less or more secure? What are the threats and what are the best practices to protect against those threats?

I’ve always found these sessions to be quite enjoyable to do and have always enjoyed the dialogue that frequently happens with questions. I encourage you to register and participate.

If you can’t join live, US Telecom will be making an archive of the session available for 90 days. I believe it will be linked from the webinar page, but if not I will update this post with the information.

Philippine Phone Phreakers Arrested After Funding Terrorists

CIDG

One of the big news items in telecom security this past week was the arrest in Manila of 4 men accused of defrauding AT&T of almost $2 million USD and then using those funds to finance a terrorist organization. The Philippine National Police issued a statement (annoyingly you have to scroll down to the “November 24, 2011” entry) that explained the terrorist link:

Sosa said that Kwan and the other hackers in Manila were being used by the Zamir’s terrorists group to hack the trunk-line (PBX) of different telecommunication companies including the AT&T. Revenues derived from the hacking activities of the Filipino-based hackers were diverted to the account of the terrorists, who paid the Filipino hackers on a commission basis via local banks.

The joint operation between the Philippine Criminal Investigation and Detection Group (CIDG) and the US FBI is per the statement a result of a long-standing effort within the FBI to combat this kind of fraud.

It’s not clear yet exactly how the fraud was perpetrated and whether or not there was any “VoIP” involved. Ars Technica, in a lengthy piece, “How Filipino phreakers turned PBX systems into cash machines for terrorists, indicates that the attackers used traditional attacks against PBXs to compromise voicemail systems that allow outbound calling (DISA) and then passed that list of compromised PBXs along to others who sold this access as a way to cheaply call into premium rate services (similar to 900-numbers in the US).

There’s also a note in the Ars Technica article that the attackers used good old default passwords to get into many of these PBXs. 🙁 Assuming the prosecutions move forward we will hopefully learn more as the cases go to trial.

Regardless of the precise mechanism, it’s a great reminder that people need to check the traditional security mechanisms of their PBX systems, and REMOVE/CHANGE default passwords!

If you are interested in discussing this case, it will be the topic of today’s (Dec 2, 2011) Voip Users Conference (VUC) call at 12 noon US Eastern. All are welcome to join – or to listen to the conversation later once the recording is posted.

Asterisk Remote Crash Vulnerability in SIP Channel Driver

Asterisk

The folks over at the Digium security team today released security bulletin AST-2011-012 for a remote crash vulnerability in the SIP channel drive. For info about the attack, they state only:

A remote authenticated user can cause a crash with a malformed request due to an uninitialized variable.

An assumption from this statement would be that an UNauthenticated user could not carry out this attack… but I admit to not personally knowing the SIP channel driver of Asterisk enough to be able to stand behind this conclusion.

Regardless, updates have been released in the form of new versions 1.8.7.1 and 10.0.0-rc1.

Avaya Acquires UC Security Firm and SBC Vendor Sipera Systems

Fascinating news today that Avaya has acquired Sipera Systems for an undisclosed sum. We’ve covered Sipera here on this blog any number of times over the past years as they have been one of the few firms very specifically focused on “VoIP security”, or, to be more appropriately buzzword-compliant in 2011, “Unified Communications security.” In fact, the first video podcast I did for the Blue Box Podcast (when I was doing that) way back in August 2007 was with Sipera.

Over the years Sipera has hired some truly excellent people in the field, released some useful tools, originated great research and done a great bit in general to help keep the dialog going on publicly about VoIP/UC security.

The Avaya purchase is fascinating because, as Eric Krapf noted in a NoJitter post this morning, Avaya has been OEMing a Session Border Controller (SBC) solution from market leader Acme Packet for quite some time. As Eric notes:

The deal therefore could represent a shift in the enterprise SBC market, at a moment when E-SBCs are emerging as a key component of enterprise real-time communications deployments, especially in SIP trunking deployments. Acme Packet has been far and away the market share leader in SBCs, with over 50%, and its SBC works with all the leading enterprise communications platforms.

However, enterprise vendors including Cisco and Siemens (and now, it seems, Avaya) have released their own SBCs, and in the case of Siemens, the SBC only talks to Siemens platforms on the enterprise side of the device. It remains to be seen whether the Sipera SBC will work only with Avaya Aura–but it seems unlikely that anyone other than an Avaya customer would buy an Avaya SBC.

Now, the news release of course plays up how Sipera’s solutions work with both Avaya and non-Avaya systems but to Eric’s point there may in the future be little incentive for non-Avaya customers to purchase a solution, given that there are other “independent” players out there in the SBC market like Acme Packet, Ingate Systems, Sonus Networks and others.

Regardless of how it all shakes out, it is an interesting move and one that bears watching.

Congrats to our friends at Sipera and Avaya on the acquisition, and we look forward to seeing how it evolves.