Pierluigi Paganini September 28, 2019

Researchers are warning of a new variant of recently disclosed SimJacker attack, dubbed WIBattack, that could expose millions of mobile phones to remote hacking.

WIBattack is a new variant of the recently discovered Simjacker attack method that could expose millions of mobile phones to remote hacking.

A couple of weeks ago, cybersecurity researchers at AdaptiveMobile Security disclosed a critical vulnerability in SIM cards dubbed SimJacker that could be exploited by remote attackers to compromise targeted mobile phones and spy on victims just by sending an SMS.

The SimJacker vulnerability resides in the S@T (SIMalliance Toolbox) Browser dynamic SIM toolkit that is embedded in most SIM cards used by mobile operators in at least 30 countries. The experts discovered that that the exploitation of the vulnerability is independent of the model of phone used by the victim.

The scary part of the story is that a private surveillance firm was aware of the zero-day flaw since at least two years and is actively exploiting the SimJacker vulnerability to spy on mobile users in several countries.

Following the disclosure of the Simjacker attack, the researcher Lakatos from Ginno Security Lab discovered that another dynamic SIM toolkit, called Wireless Internet Browser (WIB), can be exploited in a similar way.

Lakatos first discovered this vulnerability back in 2015, but he did not publicly disclose the flaw is hard to patch and it could be abused by threat actors to remotely take over the phones running vulnerable SIMs.

“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.” reads a blog post published by the researcher.

“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 researcher also claimed to have discovered the flaw in S@T Browser and disclosed a video PoC of the Simjacker with details that have not yet been published by AdaptiveMobile Security researchers.

The flaw in both S@T and WIB Browsers can be exploited to perform several malicious tasks by sending an SMS containing a spyware-like code.

Back to the WIBattack, the WIB toolkit was created by SmartTrust, a company that provides SIM toolkit-based browsing solutions hundreds of mobile operators worldwide, including AT&T, Etisalat, KPN, TMobile, Telenor, and Vodafone.

Like the S@T Browser, WIB toolkit has also been designed to allow mobile carriers to provide some essential services, subscriptions, and value-added services over-the-air to the customers. It also allows changing core network settings on their devices.

“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,” continues the researcher.

The flaw in the WIB toolkit could be exploited to:

• Retrieve the target device’ location and IMEI
• Send fake messages on behalf of victims,
• Distribute malware by launching victim’s phone browser and visiting a malicious web page
• dial premium-rate numbers
• Call the attacker’s phone number to spy on victims’ surroundings via the device’s microphone
• Perform denial of service attacks by disabling the SIM card
• Retrieving target device info (i.e language, radio type, battery level, etc.)

Below the attack scenario described by the expert:

(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).

The researcher published a video PoC of the attack:

Lakatos shared his findings on WIBAttack with the GSM Association (GSMA).
Summarizing, at least two hacking techniques leverage vulnerabilities in one of the components of most of the mobile SIM cards of the market potentially exposing billions of mobile users at attacks.

The researcher announced that is working on a mobile phone app that would allow users to scan their SIM cards to determine if they are vulnerable to the Simjacker attack.

The researchers at SRLabs also developed an Android app, named SnoopSnitch, that can detect Simjacker-like attacks. The SnoopSnitch app only runs on rooted Android mobile phones with a Qualcomm chipset.

“The SnoopSnitch Android app warns users about binary SMS attacks including Simjacker since 2014. (Attack alerting requires a rooted Android phone with Qualcomm chipset.)” reported SRLLabs.

Pierluigi Paganini

(SecurityAffairs – WIBattack, hacking)

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