Category Archives: Security

SS7 Security On Techmeme? A Reminder About Interconnected Systems…

techmeme-ss7SS7 security issues reported on Techmeme?  I did a double-take yesterday and, as Jay Cuthrell noted on Twitter, wondered if this was a “ThrowbackThursday” taken to the extreme.  But no, there was indeed a report in the Washington Post about German security researchers discovering that aspects of SS7 signaling that could be used to listen to phone conversations and/or read text messages on mobile networks.  As the article notes:

The flaws discovered by the German researchers are actually functions built into SS7 for other purposes – such as keeping calls connected as users speed down highways, switching from cell tower to cell tower – that hackers can repurpose for surveillance because of the lax security on the network.

The researchers noted that one of the attackers could get around existing encryption mechanisms used on mobile networks:

For calls or texts transmitted using strong encryption, such as is commonly used for advanced 3G connections, hackers could request through SS7 that each caller’s carrier release a temporary encryption key to unlock the communication after it has been recorded.

SS7, or Signalling System 7, is of course the dominant set of telephony signaling protocols used in the legacy Public Switched Telephone Network (PSTN) made up of today’s wired and wireless (mobile) telephone networks.  As such, we don’t write about SS7 hardly at all here on the VOIPSA blog as it is not related to VoIP.

However, there were three important thoughts to me coming out of this article:

1. VoIP can be more secure than the PSTN. The report mentions the encryption of the underlying 3G transport infrastructure being subverted.  However, with VoIP apps that are “Over-The-Top” (OTT) riding on the mobile data network, the encryption can happen from within the app on one mobile device all the way to the app on the other mobile device – or at least back to a central set of servers.  Now, there can be other security vulnerabilities with such a system, but the transport layer could at least be secured.

2. Telecommunication systems are only as secure as their weakest link – and are interconnected.  The bigger concern is of course that most of our telecom systems are all interconnected… and you can have the most secure VoIP system in the world, but if you wind up connecting to the PSTN – and specifically in this case to mobile PSTN networks – then you are open to exactly these kind of attacks.  Obviously if you are communicating only within an OTT “walled garden” where you only talk to others using the same OTT app you can be secure, but the moment you go out to the PSTN you are open to all the issues there.

3. Fixed lines are no safer if you talk to mobile users. The article ends with a German senator saying “When I really need a confidential conversation, I use a fixed-line phone“.  I don’t know about that.  For one thing, if the person you are calling is a mobile phone user, you are again open to these kind of attacks.  Secondly the Snowden revelations of the past year have certainly shown us that large agencies have the ability to listen in to communications on the networks of the PSTN.  If I absolutely want a confidential conversation, I’m personally going to use one of the VoIP applications that has end-to-end encryption. I’m NOT going to trust a fixed line any more than I would trust a mobile phone.

And I guess the final thought is of course that the legacy PSTN is full of security issues – they just aren’t necessarily as open to all to see because of the more closed nature of the traditional telephone networks.

A good reminder, though, that telephony security has always been a problem – and we need to ensure that both our VoIP and traditional networks have adequate security.

Meanwhile, it was rather fun to see SS7 mentioned on Techmeme… not something you’d expect to see!

Slides: Reboot the Open Realtime Revolution – #MoreCrypto (Fall 2014)

Olle Johansson is back with another set of excellent slides about VoIP security and the need to have “MoreCrypto” everywhere. It’s a great set of slides that talks about where we have come from and where we need to go.  Definitely check it out on SlideShare at: Reboot the Open Realtime Revolution – #MoreCrypto (Fall 2014) or in the embedded version below:

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.

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?

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.

VoIP Fraudster Pleads Guilty to $4.4 Million USD Theft of Services from AT&T, Verizon, Others

FbiNews out of the U.S. Federal Bureau of Investigation (FBI) last week was that a New Jersey man pled guilty to charges that he and his co-conspirators stole over $4.4 million USD of VoIP services from a range of VoIP service providers including AT&T, Verizon and many others.

Reading through the FBI news release, the scam really has nothing to do with “VoIP security”, per se, and everything to do with “social engineering.” Essentially, the group managed to appear to be a legitimate business so that VoIP service providers would let them resell their services to businesses. They then resold that service and pocketed the money without ever paying the service providers.

From the news release, it seems to have been a rather extensive scam:

To make it appear as if the shell companies were legitimate VoIP wholesalers and to induce the victim providers to extend credit to the companies on favorable terms, Tonangi and his co-conspirators took several fraudulent steps, including establishing fake business addresses for the shell companies at prominent New York locations, including the Empire State Building.

The co-conspirators also used Internet-based answering services that purported to connect callers to the shell companies’ various departments, such as accounts receivable and marketing, but really connected to cell phones controlled by the co-conspirators.

Tonangi and his co-conspirators created shell company e-mail accounts in the names of non-existent employees for communicating with victim providers; websites that contained false information, such as the names of non-existent employees and the companies’ fabricated qualifications to serve as VoIP wholesalers; and aliases to negotiate the purchase of VoIP services.

They also fabricated year-end financial reports that bore the logo of a national accounting firm in order to give the appearance that the shell companies’ financial reports had been reviewed by that firm.

When the victim providers sold VoIP services to the shell companies on credit, Tonangi and his co-conspirators would “bust out” the account by causing the companies to use substantially more VoIP services than the companies had been approved to buy in such a short period of time. The co-conspirators would do this over weekends and holidays so that the providers would not notice.

When the invoices for the services came due, the co-conspirators would send fake wire transfer confirmations via e-mail or submit small payments to keep the victim providers from cutting off service.

If victim providers sued or threatened to sue the shell companies, Tonangi and his co-conspirators would respond in legal pleadings or letters that they prepared in the name of a non-existent attorney, Frank Soss. Tonangi and Bhambhani created and used a fraudulent United States passport in the name Frank Soss by downloading and altering a exemplar passport image and photograph from the Internet.

Given the degree of subterfuge undertaken by the group, I’m not at all surprised that they fooled numerous companies into extending credit for VoIP services. When you are doing due diligence on a new customer, you would explore many of the avenues that these folks seem to have covered.

It’s not clear from the news release or any other information I’ve seen online what if any VoIP technology was used here but given that the group was acting as a legitimate business they didn’t need anything very sophisticated. Many software and service options would have met their needs.

It’s good to see the FBI successfully cracking this fraud ring… sadly I’m sure there will be others as we see the increased usage of VoIP across the industry.

P.S. Thanks to J. Oquendo in the VOIPSEC mailing list for alerting us to this news from the FBI.

Voipscanner.com – a hosted service for scanning IP-PBXs

VoipscannerThis week at the SIPNOC event near DC, an attendee asked if I knew of any hosted services that would scan the external interface of a network to see if the VoIP services were secure. He sells SIP connectivity to small businesses, many of whom typically have purchased an IP-PBX from somewhere like a retail store and have minimal IT expertise. He wondered if there was a service he could refer these small businesses to so that they could check the security of their system. Basically something for VoIP along the lines of hosted services like “Shields Up” that will check the security of your firewall.

I didn’t know of such a service, but posted the question to the VOIPSEC mailing list. A couple of people contacted me privately about some services in the works, but then someone did pass along a link to a public service available now:

https://voipscanner.com/voipscanner/

Now, I’ve not used this service but I’m certainly aware of Sandro Gauci and a number of the different tools he has been working on, including SIPVicious and VOIPPACK. After watching his short video and seeing the sample report, this definitely looks like an interesting service.

Of course, with any hosted service my security paranoia is heightened and I want to know what will be done with my data. Will the scan of my IP-PBX be recorded on the Voipscanner.com servers? Will a copy of my report be saved there? Basically… can I trust the site? In looking through the terms of service after you click the graphic to “apply” for access I didn’t see any wording around this… but it’s also Friday and I’m tired… I could have missed it.

Anyway, this service is out there and for those of you comfortable with using such a service it may be useful for you. If you know of other similar services I’d also love to hear about them.

At Enterprise Connect This Week? The NSA Wants To Talk To You

Nsaboothentconnect2011If you have been at the Enterprise Connect show this week in Orlando, Florida, one of the perhaps unexpected booths on the exhibit hall floor was that of the National Security Agency (NSA). The booth was staffed by two great guys (who rapidly moved away when I raised my iPhone camera) who explained that they were there as part of the agency’s “Commercial Solutions Center” looking to find commercial technology that can help with the secure mobile solutions they are looking to deploy for the NSA.

One of the NSA staff will be on a Enterprise Connect communications security panel at 9:00am in the “Sun B” room of the Gaylord Palms tomorrow (Thursday, March 3, 2011). They are also hosting a private meeting tomorrow at the Gaylord Palms from 1-3pm for people interested in learning more. The best way to find out more about that meeting would probably be to attend the 9am session. (They were promoting details at their booth, too, but the exhibit area is now closed.)

UPDATE: The session today (March 3, 2011) will be in “Emerald 8” at the Gaylord Palms in Orlando from 1-3pm.

Good to see the NSA reaching out to the commercial sector and when more information is available about their program (they said it would be soon) I’ll update this post.

Video Summary of RSA Conference

I was not out at this year’s RSA Conference, but was following some of the conversation via Twitter. I noticed a number of good videos coming out of the event, and liked this “summary” video from David Sparks that does give an overview of some of the major themes:

David was out there on behalf of Tripwire, Inc, and produced a number of other good video interviews. I enjoyed this one with my friend Martin McKeay of the Network Security Podcast on the topic of “why is ‘cloud security’ so over hyped?”

Tekelec Blog – DNS and SIP: Threats and Protection

Over on the Tekelec blog today, Dorgham Sisalem writes on “DNS and SIP: Threats and Protection“, an area of discussion that, quite frankly, hasn’t really received much attention. DNS plays a vital role in VoIP and unified communications, and so the security around DNS and SIP definitely deserves consideration. The post is not too long, so rather than summarize, I’ll just point you over there…

Dnsandsip