Pierluigi Paganini May 04, 2017

The company O2-Telefonica in Germany has confirmed to Süddeutsche Zeitung agency that some of its customers suffered cyber heists exploiting the SS7 flaws.

Security experts have been warning for years about security vulnerabilities affecting the SS7 protocol widely adopted in mobile communications.

SS7, aka Signalling System No. 7, is a set of protocols used in telecommunications ever since the late 1970s, enabling smooth transportation of data without any breaches.

The flaws could be used by hackers to spy on targets by redirecting incoming calls, to track a phone’s location, and text messages to their devices.

Attacks exploiting vulnerabilities in the SS7 protocols could allow attackers to bypass any authentication process of principal web services (e.g. Facebook, WhatsApp) that leveraging on SMSs to identify the users.

In December 2014, a group of German researchers at the Chaos Communication Hacker Congress revealed the existence of serious security issues in the protocol used by a large number of carriers of mobile telephony. Despite the huge investment in security made by telco companies, the adoption of flawed protocols exposes customers to serious privacy and security risks.

“It’s like you secure the front door of the house, but the back door is wide open,” said Tobias Engel, one of the German researchers.

Figure 1 – Tobias Engel Slides presented at CCC Berlin

What does the network know about your location?

Tobias explained that the network knows the location of the cell tower that could be used to have a pretty good approximation of a user’s location. Despite the access to the information managed by operators is restricted to the technical operation of the network, voice calls, and short messages can be initiated to your phone number from almost anywhere in the global SS7 network.

Figure 2 – Tobias Engel Slides presented at CCC Berlin

Attacks relying on these security issues already happened in the past, one of the major incidents was registered by the NKRZI (which is the National Commission for the State Regulation of Communications and Informatization in Ukraine) and involved Russian addresses back in April 2014.

The expert noticed that many Ukrainian mobile phone holders have been targeted by SS7 packets sent from Russia to track them and steal information from the mobile devices.

Back to the present, security experts are observing the first massive hacking campaign exploiting the design flaws in the SS7 protocol to drain bank accounts. Multiple sources confirmed that hackers used this technique in the past few months.

The company O2-Telefonica in Germany has confirmed to Süddeutsche Zeitung agency that some of its customers suffered cyber heists exploiting the SS7 flaws to bypass SFA authentication mechanisms.

Hackers exploited the vulnerabilities in the SS7 protocol to intercept authentication code sent by the banking services to the customers using the two-factor authentication process.

Hackers exploited a two-factor authentication system of transaction authentication numbers used by sine German banks. The attackers first conducted a spam campaign to deliver a malware on the bank customers PC in order to collect financial information (the bank account balance, login credentials, and the mobile number).

Then hackers purchased access to a rogue telecommunications provider and set up a redirect for the victim’s mobile phone number to a handset controlled by the attackers.

At night time crooks logged into victims’ bank accounts and drained them exploiting the SS7 flaws to access the account and authorize the fraudulent transactions.

This is the first publicly confirmed attack exploiting the design flaws in the SS7 protocol in Europe.

Which is a possible solution?

Telco experts propose a replacement for SS7 on 5G networks, dubbed the Diameter protocol, unfortunately also this protocol is affected by critical security holes.

Security researchers discovered that Diameter is also affected by security issues, one of them is the lack of mandatory implementation of the Internet Protocol Security (IPsec) protocol.

According to researchers from Nokia Bell Labs and Aalto University in Finland, this means that Diameter could be hacked with the same techniques that are effective against SS7.

Last year, the team of experts made several tests to evaluate attacks against users connected to the LTE network. They simulated the attacks on a test network set up by an unnamed global mobile operator. In the tests, they powered a cyber attack against UK subscribers from Finland and discovered several methods of disrupting service to users.

The researchers were able to temporarily and permanently shut down users connections, they were also able to target entire regions.

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Pierluigi Paganini

(Security Affairs – SS7, Hacking bank accounts)

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