Security

After years of warnings, mobile network hackers exploit SS7 flaws to drain bank accounts

O2 confirms online thefts using stolen 2FA SMS codes

By Iain Thomson in San Francisco

48 SHARE

Experts have been warning for years about security blunders in the Signaling System 7 protocol – the magic glue used by cellphone networks to communicate with each other.

These shortcomings can be potentially abused to, for example, redirect people's calls and text messages to miscreants' devices. Now we've seen the first case of crooks exploiting the design flaws to line their pockets with victims' cash.

O2-Telefonica in Germany has confirmed to Süddeutsche Zeitung that some of its customers have had their bank accounts drained using a two-stage attack that exploits SS7.

In other words, thieves exploited SS7 to intercept two-factor authentication codes sent to online banking customers, allowing them to empty their accounts. The thefts occurred over the past few months, according to multiple sources.

In 2014, researchers demonstrated that SS7, which was created in the 1980s by telcos to allow cellular and some landline networks to interconnect and exchange data, is fundamentally flawed. Someone with internal access to a telco – such as a hacker or a corrupt employee – can get access to any other carrier's backend in the world, via SS7, to track a phone's location, read or redirect messages, and even listen to calls.

In this case, the attackers exploited a two-factor authentication system of transaction authentication numbers used by German banks. Online banking customers need to get a code sent to their phone before funds are transferred between accounts.

The hackers first spammed out malware to victims' computers, which collected the bank account balance, login details and passwords for their accounts, along with their mobile number. Then they 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.

Next, usually in the middle of the night when the mark was asleep, the attackers logged into their online bank accounts and transferred money out. When the transaction numbers were sent they were routed to the criminals, who then finalized the transaction.

While security experts have been warning about just this kind of attack – and politicians have increasingly been making noise about it – the telcos have been glacial at getting to grips with the problem. The prevailing view has been that you'd need a telco to pull off an assault, and what kind of dastardly firm would let itself be used in that way.

That may have worked in the 1980s, but these days almost anyone can set themselves up as a telco, or buy access to the backend of one. To make matters worse the proposed replacement for SS7 on 5G networks, dubbed the Diameter protocol, also has security holes, according to the Communications Security, Reliability and Interoperability Council at America's comms watchdog, the FCC.

This first publicly confirmed attack will hopefully ginger up efforts to fix issues with SS7, at least in Europe, where Germany has a leadership position. As for the US, it might take a series of SS7 assaults before the telcos get their backsides into gear. ®

PS: A US Department of Homeland Security report this month admitted SS7 "can be exploited by criminals, terrorists, and nation-state actors/foreign intelligence organizations" to hijack messages and calls.

Basically, it's time to stop using SMS for two-factor authentication for sensitive stuff.

Sign up to our NewsletterGet IT in your inbox daily

48 Comments

Related

Hey FCC, when you're not busy screwing our privacy, how about those SS7 cell network security flaws, huh?

No one else seems to care, sniff politicians

Stingray phone stalker tech used near White House, SS7 abused to steal US citizens' data – just Friday things

Second worst stingray in history (RIP Steve Irwin)

You'll never get Huawei with this, FCC tells US telcos: Buy Chinese kit and you won't see another dime from us

Regulator will cut providers from Universal Service Fund dollars

Huawei with you! FCC's American Pai proposes rip-and-replace of scary Chinese comms kit

ZTE also on hit list

Your mobile network broke the law by selling location data and may be fined millions... or maybe not, shrugs FCC

US watchdog struggles to do its job over illegal sale of folks' whereabouts

You'e yping i wong: macOS Catalina stops Twitter desktop app from accepting B, L, M, R, and T in passwords

Oher sofwae ikey hi y egession in uggy opeaing syse

FCC proudly wastes $90m getting data-capped, pricey satellite internet to tiny percentage of US population

On the plus side, this saves cable companies the hassle of laying down fiber

Microsoft's little eyes light up as Oscar-winning Taika Waititi says Apple keyboards make him 'want to go back to PCs'

Literally just for the keyboard. Pipe down, Panos

Since the FCC won't act, Congress finally moves on robocalls by passing half-decent TRACED Act

Only took seven years of consumer hell to get this far

Satellite operators' shares plummet as FCC plumps for public 5G spectrum auctions

You win some, you lose… 75 per cent of your share value

Whitepapers

Reduce Redis Enterprise Deployment Cost, Complexity with Intel® Optane™ DC Persistent Memory

Intel and Redis Labs have prepared this kit to help you reduce Redis Enterprise deployments cost and complexity with 2nd Generation Intel® Xeon® Scalable processors and Intel® Optane™ DC persistent memory.

How to Build Your Digital Experience Portfolio

In this session, Michael Facemire, Forrester VP & Principal Analyst at Forrester will cover how a digital experience portfolio strategy can help IT teams deliver new experiences

CEO Fraud Prevention Manual

CEO fraud has ruined the careers of many executives and loyal employees. Don’t be one of them.

Who Needs Malware?

Learn how fileless techniques work and why they present such a complex challenge.