Lakatos – Chief Researcher of Ginno Security Laboratory
We researched security in simcard and discovered the vulnerability in WIB simcard-browser that causes serious harm to hundreds of millions of telecom subscribers worldwide in 2015, and the vulnerability has not ever been published yet.
By sending a malicious SMS to victim phone number, attacker can abuse the vulnerabilities in the WIB sim browser to remotely take control of the victim mobile phone to perform harmful actions such as: send sms, make phone call, get victim’s location, launch other browsers (e.g WAP browser), get victim’s IMEI, etc.
The affection of the vulnerability in WIB spreads worldwide and puts hundreds of millions of telecom subscribers worldwide at risk. The security vulnerability comes from sim card, depends neither on mobile phone devices nor on mobile phone Operating System, so every mobile phone is affected.
1. What is WIB?
As an alternative to static SIM toolkit applications with a fixed pre-installed menu, some operators opt for dynamic SIM toolkit, where the menus and user dialogs are generated on the fly based on information provided by a central server. SIM applications that provide this functionality are generally referred to as SIM-browsers or µ-browsers.
Two browsers are currently available, the Wireless Internet Browser (WIB) which was the first successful browser released and promoted on the market by SmartTrust.
The Wireless Internet Browser (WIB) is specified by SmartTrust and is the market leading solution for SIM toolkit based browsing. The WIB-enabled SIM has a menu stored on the SIM. This menu can be managed and updated using Over The Air (OTA) services.
2. How much popular is the dynamic SIM toolkit (WIB) in the market?
“SmartTrust is a leading provider of infrastructure solutions designed to enable secure mobile e-services. More than 85 mobile operators worldwide are using SmartTrust technology to diversify their service offerings and open new revenue streams by launching enhanced SMS services, controlling mobile end-user applications and managing the entire life cycle of the SIM/USIM.” 
“Operators of more than 200 networks worldwide including AT&T, Claro, Etisalat, KPN, TMobile, Telenor, and Vodafone rely upon SmartTrust technology to address the unique business challenges of today’s mobile markets. With a complete portfolio of products and services, which facilitate the management of the entire lifecycle for SIMs, handsets and services as well as Dynamic Roaming Steering, SmartTrust delivers the tools for successfully managing the subscriber experience.”  
3. In Details
3.1. Attack Scenario
Attack Scenario is summarized in figure.
(1) Attacker sends a malicious OTA SMS to the victim phone number. The OTA SMS contains WIB command such as: SETUP CALL, SEND SMS, PROVIDE LOCATION INFO, etc.
(2) Right after receiving the OTA SMS, Baseband Operating System of the victim mobile phone uses ENVELOP COMMAND ( an APDU command to communicate between mobile phone and simcard) to forward the TPDU of the OTA SMS to WIB browser in victim’s simcard.
Different from the procedure of receiving the normal text sms, the procedure OTA SMS is silently handled just in baseband operating system and does not raise any alert to application operating system (android os, ios, blackberry os, …). Neither feature phone nor smart phone raises alert about the procedure of ota sms: no ringing, no vibration, no detection from users.
(3) WIB browser follows the WIB commands inside the TPDU of OTA SMS and sends the corresponding PROACTIVE COMMAND to the victim mobile phone such as: SETUP CALL, SEND SMS, PROVIDE LOCATION INFO.
(4) The victim mobile phone follows the PROACTIVE COMMAND received from victim’s simcard to perform the corresponding actions such as: make a phone call, send an sms to whatever phone number attacker wants (e.g receiver mobile phone in the figure).
For attack scenario of getting victim’ location, it contains 2 phases in a single malicious OTA SMS. First phase, the ota sms instructs the WIB browser send PROACTIVE COMMAND ( PROVIDE LOCATION INFO) to the victim mobile phone. Second phase, instructs the WIB browser to send a PROACTIVE COMMAND (SEND SMS) with sms payload containing the response from the victim mobile phone (Cell ID, Lac ID). Attacker can use many websites on internet to convert the Cell ID, Lac ID to gps location on map.
3.2 WIB Commands
Several sensitive WIB commands which can send remotely via OTA SMS to victim’s sim card.
3.3. Proactive Command
The concept of Proactive command is described in detail in specification 3GPP TS 11.14.
“TS 11.11  defines that the ME communicates to the SIM using the T=0 protocol, which is specified in ISO/IEC 7816‑3 . The ME is always the “master” and initiates commands to the SIM, and therefore there is no mechanism for the SIM to initiate a communication with the ME. This limits the possibility of introducing new SIM features requiring the support of the ME, as the ME needs to know in advance what actions it should take”
“The proactive SIM service provides a mechanism which stays within the protocol of T=0, but adds a new status response word SW1. This status response has the same meaning as the normal ending (’90 00′), and can be used with most of the commands that allow the normal ending, but it also allows the SIM to say to the ME “I have some information to send to you”. The ME then uses the FETCH function to find out what this information is.”
“The SIM can issue a variety of commands through this mechanism, given in alphabetical order:
– DISPLAY TEXT, which displays text or an icon on screen. A high priority is available, to replace anything else on screen.
- LAUNCH BROWSER, which requests a browser inside a browser enabled ME to interpret the content corresponding to a URL.
– OPEN CHANNEL, which requests the ME to open a data channel with parameters indicated in the command (if class “e” is supported.)
– PLAY TONE, which requests the ME to play a tone in its earpiece, ringer, or other appropriate loudspeaker.
– PROVIDE LOCAL INFORMATION which requests the ME to pass local information to the SIM, for example the mobile country and network codes (MCC + MNC) of the network on which the user is registered.
– SEND SHORT MESSAGE, which sends a short message or SMS-COMMAND to the network.
– SEND SS, which sends an SS request to the network.
– SEND USSD, which sends a USSD string to the network.
– SET UP CALL, of which there are three types:
– set up a call, but only if not currently busy on another call;
– set up a call, putting all other calls (if any) on hold;
– set up a call, disconnecting all other calls (if any);
 3GPP TS 11.14 V8.18.0 (2007-06)
3.4. Security mechanisms of OTA SMS
OTA (Over-The-Air) is a technology used to communicate with, download applications to, and manage a SIM card without being connected physically to the card.
OTA enables a Network Operator to introduce new SIM services or to modify the contents of SIM cards in a rapid and cost-effective way.
OTA is based on client/server architecture where at one end there is an operator back-end system (customer care, billing system, application server … ) and at the other end there is a SIM card.
The operator’s back-end system sends service requests to an OTA Gateway which transforms the requests into Short Messages and sends them onto a Short Message Service Centre (SMSC) which transmits them to one or several SIM cards in the field.
Thus, Over-The-Air (OTA) is a technology that updates and changes data in the SIM card without having to reissue it. Indeed, the end user can receive special messages from the operator, download or activate new services on his telephone, and much more …, without having to return to a retail outlet.
In order to implement OTA technology, the following components are needed:
- A back end system to send requests
- An OTA Gateway to process the requests in an understandable format to the SIM card
- An SMSC to send requests through the wireless network
- A bearer to transport the request: today it is the SMS bearer
- Mobile equipment to receive the request and transmit it to the SIM card
- A SIM card to receive and execute the request
However, OTA SMS can also be sent from peer to peer, i.e from mobile subscriber to mobile subscriber.
The protection settings/Security Level of OTA Command packet is indicated by the first byte of SPI (header of OTA SMS). MSL = 0 means that the Command packet of the OTA SMS is not applied any security protection at all such as: No counter available, no ciphering, no redundancy check, no crypto-checksum, no Digital Signature. When simcard receives the OTA SMS, it will compare the MSL of OTA SMS with the MSL configured in simcard. If the MSL of OTA SMS is less than the MSL configured in simcard, simcard will discard the Command packet and may be send response to the sent entity (OTA Server or the phone number Originating Address in the received OTA SMS ).
MSL can be configured the same for all application in simcard or can be differently configured for each individual sim application ( application ID is indicated by TAR header of OTA SMS).
So, the key-points of the attack is:
- Security mechanism of OTA SMS can be breakable:
- If the WIB is configured with MSL = 0 or with other MSL values that do not need KiC/KiD, attacker can send OTA SMS Command in to control the WIB without knowing OTA key KiC, KiD.
- Attacker can applied the attack “rooting simcard”  (Famous Security Expert Dr.Karsten Nohl – Security Research Lab Berlin) to crack key KiC, KiD. Then he uses the cracked ota key KiC, KiD to authorized his OTA SMS Command to control WIB.
- Protection of KiC, KiD might be not secured, it depends on sim vendor, telco network, OTA server. Hackers could target on them, and got OTA key. 
- WIB supports many sensitive Commands: Setup call, Provide Location, Send SMS, launch browsers, …. And the commands can be instructed to execute remotely just via SMS. Their execution is in silently without any notification to victim. The malicious SMS be sent globally from anywhere.
- All security and protection mechanism of application OS, antivirus application do not work at all in the situation. Sim card is a hidden OS with hidden applications. Except sim vendor, no one knows how many sim applications there is in the simcard, what is it used for? How it works? Is it safe and secured for subscriber?. Can it be remotely controlled? Simcard is a blackbox. Sim vendor has not published their OS.
In the demo, attacker will send a malicious sms (an OTA SMS) to the victim phone number. The malicious sms will control the victim mobile phone send an SMS to the receiver.
We already reported the vulnerability in WIB to The GSM Association
- SMS Home Routing
- Filter OTA SMS.
- OTA update to simcard to update MSL or to remove WIB.
- Should have security guideline & sim-scanning tool to check security of simcard sample before buying simcards from sim bidders/vendors.
- if the simcard got vulnerabilities, should change new secured simcard for subscribers to protect them completely.
b) Enduser sides:
- You scan simcard to check if your sim is secured or not.
We have already discussed the vulnerabilites in WIB with the security expert Mr. Luca Melette (famous security expert from Security Research Lab) since March 2019. https://srlabs.de/bites/sim_attacks_demystified/
Mr. Luca Melette and me already worked together to apply a patch for SIMtester that scan vulnerabilities in WIB browser. The new version of SIMTester is already released by SRlabs at https://opensource.srlabs.de/projects/simtester
Beside, we are developing a sim-scanning tool that can run on android devices to support more many people who dont have sim card reader.
- If your sim card got vulnerabilities, you should buy a secured simcard to protect you 100%. because network could not protect the unsecured simcard when you go roaming to other network.
We also inherited and modified SIMtester for scanning the sim-browser vulnerabilities in 2015. Following is some result-log file of fuzzing WIB and testing S@T in 2015
6. About us
We are passionate Security Researchers from Ginno Security Lab, a non-profit organization. We had some reasons that cause us to keep the vulnerabilities in secrete in many years. All the reason is for protecting subscribers because it is very hard to protect subscribers completely. Now something changes our mind, security should be published for everyone know and raise awareness to protect them.
We would like to express our big appreciation to the famous security expert Luca Melette and other security experts from the famous Security Research Labs. The presentation “Rooting Simcard – Black Hat 2013” of the famous security expert Dr. Karsten Nohl gave us inspiration to research security in Simcard in 2015. Security Research Labs is the pioneer to discover hidden protocol inside simcard. We learned a lot from the presentation. We also inherited and modified their valuable sim-scanning tool “SIMtester” in our research.