Tag Archive for MITM

Scary SS7 Flaw Strikes Banks

Scary SS7 Flaw Strikes BanksLost in last month’s hub-bub over WannaCry ransomware was the revelation that hackers had successfully exploited the SS7 “flaw” in January 2017. In May reports surfaced that hackers were able to remotely pilfer German bank accounts by taking advantage of vulnerabilities in Signaling System 7 (SS7). SS7 is a standard that defines how to public phone system talks to itself to complete a phone call.

Telephone system Signaling System 7 The high-tech heist was initially reported by the German newspaper Süddeutsche Zeitung (auf Deutsch). The attack was  a sophisticated operation that combined targeted phishing emails and SS7 exploits to bypass two-factor authentication (2FA) protection. This is the first publicly known exploit of SS7 to intercept two-factor authentication codes sent by a bank to confirm actions taken by online banking customers.

According to ars technica the attack began with traditional bank-fraud trojans. These trojans infect account holders’ computers and steal the passwords used to log in to bank accounts. From there, attackers could view account balances, but were prevented from making transfers without the one-time password the bank sent as a text message. After stealing the necessary login details via phishing emails, the perpetrators leveraged the SS7 flaw to intercept the associated mTAN (mobile transaction authentication numbers) authentication codes sent to the victims — messages notifying them of account activity — to validate the transactions and remain hidden, investigators say.

Central office equipmentGerman Telecommunications giant O2-Telefonica confirmed details of the SS7-based cyber attacks to the newspaper. Ars says, in the past, attackers have obtained mTANs by obtaining a duplicate SIM card that allows them to take control of the bank customer’s phone number. SS7-facilitated compromises, by contrast, can be done remotely on a much larger quantity of phone numbers.

O2 Telefonica confirmed to Help Net Security that the attackers were able to gain access to the network of a foreign mobile network operator in January 2017. The attackers likely purchased access to the foreign telecommunications provider – this can apparently be done for less than 1,000 euros – and have set up call and SMS forwarding.

Ford Road CO in Dearborn Mi is the Oregon officeTwo-factor authentication (2FA) is a security process in which the user provides two authentication factors to verify they are who they say they are.  2FA provides an extra layer of security and makes it harder for attackers to gain access to a person’s devices and online accounts, because knowing the victim’s password alone is not enough to pass the authentication check. Two-factor authentication has long been used to control access to sensitive systems and data, and online services are increasingly introducing 2FA to prevent their users’ data from being accessed by hackers who have stolen a password database or used phishing campaigns to get users’ passwords.

News of the incident prompted widespread concern online. Security advocates railed against the popular and continuous use of text messages to authenticate account information while growing evidence suggests that SS7 is an unsafe channel to deliver such data. Security experts told ars that the same SS7-centric hacking techniques used against German banks will become increasingly prevalent in the future, forcing organizations to reconsider how they authenticate user activity.

Cris Thomas, a strategist at Tenable Network Security warns in the article:

Two-factor authenticationWhile this is not the end of 2FA, it may be the end of 2FA over SS7, which comprises a majority of 2FA systems … Vulnerabilities in SS7 and other cellular protocols aren’t new. They have been presented at security conferences for years … there are other more secure protocols available now that systems can switch to…

Cyber security researchers began issuing warning about this flaw in late 2014 about dangerous flaws in SS7. I wrote about the SS7 flaw in September of 2016  and in March 2107. Maybe this will be the wake up call for the carriers. One industry insider quipped:

This latest attack serves as a warning to the mobile community about what is at stake if these loopholes aren’t closed … The industry at large needs to go beyond simple measures such as two-factor authentication, to protect mobile users and their data, and invest in more sophisticated mobile security.

man-in-the-middle attackIn 2014 security researchers first  demonstrated that SS7 could be exploited to track and eavesdrop on cell phones. This new attack is essentially a man-in-the-middle attack on cell phone communications. It exploits the lack of authentication in the communication protocols that run on top of SS7.

Developed in 1975, today, over 800 telecommunications companies around the world, including AT&T (T) and Verizon (VZ), use SS7 make sure their networks interoperate. This technology has not kept up with modern times.  In May 2017, Wired published an article which explains some of the ways to secure SS7. Overcoming SS7 insecurity requires implementing a series of firewalls and filters that can stop the attacks. Researchers Wired spoke to suggest that adding encryption to SS7 would shield network traffic from prying eyes and bolster authentication. Both of these changes are unpopular with the carriers, because they cost money and can impact the network core, so don’t expect any network changes to address the SS7 flaw anytime soon.

Carriers should use SS7 firewall to secure the SS7 networkThe Register reports that the FCC’s Communications Security, Reliability and Interoperability Council found that the proposed replacement for SS7 on 5G networks, dubbed the Diameter protocol has security holes too.

In March 2017, Oregon Sen. Ron Wyden and California Rep. Ted Lieu sent a letter to Homeland Security’s John Kelly requesting that DHS investigate and provide information about the impact of SS7 vulnerabilities to U.S. companies and governmental agencies. Kelly has not responded to the letter, according to the Wired article.

Of course the TLA’s would never use this “flaw” in SS7 to spy on us.

The Guardian says that given that the SS7 vulnerabilities reside on systems outside of your control, there is very little you can do to protect yourself beyond not using the services.

PoliticianThey recommend for text messages, avoiding SMS and instead using encrypted messaging services such as Apple’s (AAPL) iMessage, Facebook‘s (FB) WhatsApp or the many others available will allow you to send and receive instant messages without having to go through the SMS network to protect your messages from surveillance.

For calls, the Guardian recommends using a service that carries voice over data rather than through the voice call network. This will help prevent your calls from being snooped on. Messaging services including WhatsApp permit calls. Silent Circle’s end-to-end encrypted Phone service or the open-source Signal app also allow secure voice communications.

protect yourself Your location could be being tracked at any stage when you have your mobile phone on. The only way to avoid it is to turn off your phone or turn off its connection to the mobile phone network and rely on Wi-Fi instead.

Related articles

Ralph Bach has blogged from his Bach Seat about IT, careers and anything else that catches his attention since 2005. You can follow me at Facebook and Twitter. Email the Bach Seat here.

Another Hole in Internet Armor

Another hole in our Internet armor has been discovered. The hole is in the Diffie-Hellman key exchange, a popular cryptographic algorithm that allows Internet protocols to agree on a shared key and negotiate a secure connection. It is fundamental to many protocols including HTTPS, SSH, IPsec, SMTPS, and protocols that rely on TLS.

 key exchange Researchers from the University of Michigan, Inria, Microsoft Research, Johns Hopkins University and the University of Pennsylvania have uncovered several weaknesses in how Diffie-Hellman key exchange has been deployed. In what they are calling the Logjam attack the DF flaw allows a man-in-the-middle attacker to downgrade vulnerable TLS connections to 512-bit export-grade cryptography. This allows the attacker to read and change any data passed over the connection.

The problem, according to the researchers, is that millions of HTTPS, SSH, and VPN servers all use the same prime numbers for Diffie-Hellman key exchange. Practitioners believed this was safe as long as new key exchange messages were generated for every connection. However, the first step in the number field sieve—the most efficient algorithm for breaking a Diffie-Hellman connection—is dependent only on this prime. After this first step, an attacker can quickly break individual connections.

Prime numbersTo prove this hypothesis, the researchers carried out this computation against the most common 512-bit prime used for TLS and demonstrated that the Logjam attack can be used to downgrade connections to 80% of TLS servers supporting DHEEXPORT.

They also estimated that an academic team can break a 768-bit prime and that a nation-state can break a 1024-bit prime. Breaking the single, most common 1024-bit prime used by web servers would allow passive eavesdropping on connections to 18% of the Top 1 Million HTTPS domains. A second prime would allow passive decryption of connections to 66% of VPN servers and 26% of SSH servers.

VPNThere is speculation that this “flaw” was being exploited by nation-state bad actors. A close reading of published NSA leaks shows that the agency’s attacks on VPNs are consistent with having created, exploited, harnessed the Logjam vulnerability.

What should you do?

1 – Go to the researchers website https://weakdh.org/ to see if your browser is secure from the Logjam flaw. (It reported that Google Chrome Version 43.0.2357.81 (64-bit) on OSX 10.10.3 was not secure}

2 – Microsoft (MSFT) patched the Logjam flaw on May 12 with security bulletin MS15-055. A Microsoft spokesperson told eWEEK;

Customers who apply the update, or have automatic updates enabled, will be protected. We encourage all customers to apply the update to help stay protected.

3 – Google (GOOG) fixed the issue with the Chrome 42 update, which debuted on April 15. Google engineer Adam Langley wrote;

We disabled TLS False-Start with Diffie-Hellman (DHE) in Chrome 42, which has been the stable version for many weeks now.

Patch4 – Mozilla’s patch for Firefox isn’t out yet, but “we expect it to be published in the next few days,” Richard Barnes, cryptographic engineering manager at Mozilla, told eWEEK.

5 – DarkReading reports that on the server-side, organizations such as Apache, Oracle (ORCL), IBM (IBM), Cisco (CSCO), and various hosting providers have been informed of the issue. There has been no response from these tech titans.

The researchers have also provided guidance:

  1. If you have a web or mail server, they recommend  – disable support for export cipher suites and generate a unique 2048-bit Diffie-Hellman group. They have published a Guide to Deploying Diffie-Hellman for TLS with step-by-step instructions.
  2. If you use SSH, you should upgrade both your server and client installations to the most recent version of OpenSSH, which prefers Elliptic-Curve Diffie-Hellman Key Exchange.
  3. If you’re a sysadmin or developer, make sure any TLS libraries you use are up-to-date, that servers you support use 2048-bit or larger primes, and that clients you maintain reject Diffie-Hellman primes smaller than 1024-bit.

rb-

Finally, get involved. Write someone, your representative, senator, your favorite bureaucrat, the president, your candidate and tell them to get out-of-the-way. 

Ars Technica notes that Logjam is partly caused by export restrictions put in place by the US government in the 1990s, to allow government agencies the ability to break encryption used in other countries. “Logjam shows us once again why it’s a terrible idea to deliberately weaken cryptography, as the FBI and some in law enforcement are now calling for,” said Michigan’s J. Alex Halderman to the report. “Today that backdoor is wide open.”

 

Ralph Bach has been in IT for fifteen years and has blogged from his Bach Seat about IT, careers and anything else that catches his attention since 2005. You can follow me at Facebook and Twitter. Email the Bach Seat here.