Feeds

Mobiles forced to send premium-rate texts in new attack

Hacker hijacks SMS error message flaw

High performance access to file storage

Cybercrooks may be able to force mobiles to send premium-rate SMS messages or prevent them from receiving messages due to security weaknesses in mobile telecoms standards.

The weakness involves the handling of messages directed towards SIM Application Toolkits, applications preloaded onto SIM cards by mobile operators. The applications can be used for functions such as displaying available credit or checking voicemail, as well as handling value-added services, such as micro-payments.

SIM Toolkits receive commands via specially formatted and digitally signed SMS messages. These messages are processed without appearing in a user's inbox and without triggering any other form of alert. Some mobiles may wake from a sleeping state on receipt of such messages but that is about all that's likely to happen.

The encryption scheme deployed is robust but problems might arise because error messages are automatically sent out if a command cannot be executed. The SIM Toolkit service message can be configured so that responses are made via SMS to a sender's number or to the operator's message centre. This creates two possible attack scenarios.

In the first case, an attacker might use an SMS spoofing service to force the dispatch of an error message to a premium-rate number, potentially ringing up fraudulent charges against the account of a targeted phone owner in the process.

Attackers can't control the content of the automatic error responses, a potential stumbling block when it comes to signing up people up for these services simply because they've sent a message, but it's easy to imagine this tactic will be effective enough times to make it potentially workable. A premium-rate number is restricted to signing up people to its services only in response to properly formatted requests rather than an any old message.

In the second case, an SIM Toolkit error message is sent to the operator's message centre, and this is interpreted as a message delivery failure. Operators usually attempt to resend the undelivered message: creating an error loop that prevents the delivery of legitimate SMS messages to a user's handset until a bogus SIM Toolkit message times out, typically after 24 hours or so. Because of this, sending a series of bogus SIM Toolkit messages creates a means of running an SMS DoS attack.

Independent security researcher Bogdan Alecu gave a presentation explaining the security shortcoming, and demonstrating how it might be exploited, at a recent DeepSec security conference in Vienna, Austria.

Alecu tested the attack against phones from Samsung, Nokia, HTC, RIM and Apple. Only phones from Nokia have the option to ask users before confirming the dispatch of an SIM Toolkit response. However the the option "Confirm SIM Service Actions" is usually disabled by default. Operators could mitigate the attack by filtering SIM Toolkit messages and whitelisting numbers that are allowed to send them. However Alecu said he is yet to encounter an operator that applies such controls, even after testing the attack on mobile operators in Romania, Bulgaria, Austria, Germany and France, IDG reports.

The vulnerability was reported by Alecu to the Computer Emergency Response Team and a vulnerability number has been allocated but there are no details on when a fix might be produced. Alecu said that the issue is more easily addressed by filtering by operators than by trying to update millions of handsets anyway. ®

High performance access to file storage

More from The Register

next story
Parent gabfest Mumsnet hit by SSL bug: My heart bleeds, grins hacker
Natter-board tells middle-class Britain to purée its passwords
Obama allows NSA to exploit 0-days: report
If the spooks say they need it, they get it
Web data BLEEDOUT: Users to feel the pain as Heartbleed bug revealed
Vendors and ISPs have work to do updating firmware - if it's possible to fix this
Samsung Galaxy S5 fingerprint scanner hacked in just 4 DAYS
Sammy's newbie cooked slower than iPhone, also costs more to build
Snowden-inspired crypto-email service Lavaboom launches
German service pays tribute to Lavabit
One year on: diplomatic fail as Chinese APT gangs get back to work
Mandiant says past 12 months shows Beijing won't call off its hackers
Call of Duty 'fragged using OpenSSL's Heartbleed exploit'
So it begins ... or maybe not, says one analyst
NSA denies it knew about and USED Heartbleed encryption flaw for TWO YEARS
Agency forgets it exists to protect communications, not just spy on them
prev story

Whitepapers

Securing web applications made simple and scalable
In this whitepaper learn how automated security testing can provide a simple and scalable way to protect your web applications.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
HP ArcSight ESM solution helps Finansbank
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Mobile application security study
Download this report to see the alarming realities regarding the sheer number of applications vulnerable to attack, as well as the most common and easily addressable vulnerability errors.