Metro Bank has been attacked by a Signalling Systems Number 7 (SS7) cyber-attack and has reportedly fallen victim to a sophisticated two-factor authentication (2FA) bypass SS7 attack.  The attack, which was first discovered by Motherboard and involved hackers tracking phones remotely and intercepting messages to authorise payments from accounts.  Other banks are understood to have also been affected by this attack and the UK National Security Centre says SS7 attacks are increasing in regularity.

The (SS7) protocol system is used by telecoms companies to coordinate how calls and texts are routed. Hackers were able to exploit flaws in SS7, a protocol used by telecoms companies to coordinate how they route calls and SMS messages around the world.

Ryan Gosling, head of partnerships and Telco at Callsign has told Retail Banker International that the hack on Metro is not surprising but there are some methods the banks should use for SS7.

“There have been several documented cases of SS7 breaches in the past. But, due to the underlying historical weaknesses in the technology, it has been difficult to resolve the SS7 vulnerability.

“While some effort has been made by the network operators to address the problem, some SS7 messages just cannot be filtered at the network boundaries. There are some legitimate reasons to send cross-network messages e.g. to set up call roaming.

“Therefore, if hackers can infiltrate any SS7 network, they can send certain SS7 messages to their fraud target’s home network. These can be used to set up misdirection of banking verification codes.”

SS7 Attack and Possible Solutions
Gosling says the solution is three-fold. “Firstly, banks must adopt a strong and agile governance process in terms of authentication policies. They should also regularly review these policies. Thus they are fully up to date and can adjust their authentication methods as required to mitigate new threats.

“Secondly, they must employ a proactive cybersecurity research arm. In this way they can keep track of the new attacks being made on SS7 and other legacy protocols.

“The final, and most crucial means of combatting the security issues associated with SS7 is to use an intelligence engine to spot anomalous behaviour. All banks can do is gather together as many data points as possible. That is, device, call divert, SIM swap, and roaming statuses from MNOs and specialist services.

“As a result, they build up a picture of their customers. An integrated approach should correlate this data to provide a single view of the person undertaking the transaction and the environmental circumstances around that.

“A feedback loop to the intelligence engine to inform it about known fraud cases can also help it learn about bad behaviour.  And recognise that a fraudster is at work based on similar combinations of these data points in the future.”

A Metro Bank spokesman said that a “small number” of the bank’s customers had been affected. She said: “At Metro Bank we take our customers’ security extremely seriously and have a comprehensive range of safeguards in place to help protect them against fraud. We have supported telecommunication companies and law enforcement authorities with an industry-wide investigation and understand that steps have been taken to resolve the issue.

“Of those customers impacted by this type of fraud, an extremely small number have been Metro Bank customers and none have been left out of pocket as a result. Customers should continue to remain vigilant and report any suspicious activity using the number on the back of their card or on our website.”

Metro Bank first reported the issue to authorities and apparently other businesses were affected by this cyber-attack, but they have not made public statements. 

Source:  Cyber Security Intelligence