Hackers steal WhatsApp accounts using call forwarding trick

By Ionut Ilascu, Bleeping Computer

There’s a trick that allows attackers to hijack a victim’s WhatsApp account and gain access to personal messages and contact list.

The method relies on the mobile carriers’ automated service to forward calls to a different phone number, and WhatsApp’s option to send a one-time password (OTP) verification code via voice call.

The MMI code trick

Rahul Sasi, the founder and CEO of digital risk protection company CloudSEK, posted some details about the method saying that it is used to hack WhatsApp account. 

BleepingComputer tested and found that the method works, albeit with some caveats that a sufficiently skilled attacker could overcome.

It takes just a few minutes for the attacker to take over the WhatsApp account of a victim, but they need to know the target’s phone number and be prepared do some social engineering.

Sasi says that an attacker first needs to convince the victim to make a call to a number that starts with a Man Machine Interface (MMI) code that the mobile carrier set up to enable call forwarding.

Depending on the carrier, a different MMI code can forward all calls to a terminal to a different number or just when the line is busy or there is no reception.

These codes start with a star (*) or a hash (#) symbol. They are easily found and from the research we did, all major mobile network operators support them.

“First, you receive a call from the attacker who will convince you to make a call to the following number **67* or *405*. Within a few minutes, your WhatsApp would be logged out, and the attackers would get complete control of your account” - Rahul Sasi

The researcher explains that the 10 digit number belongs to the attacker and the MMI code in front of it tells the mobile carrier to forward all calls to the phone number specified after it when the victim’s line is busy.

Once they tricked the victim into forwarding calls to their number, the attacker starts the the WhatsApp registration process on their device, choosing the option to receive the OTP via voice call.

After they get the OTP code, the attacker can register the victim’s WhatsApp account on their device and enable two-factor authentication (2FA), which prevents legitimate owners from regaining access.

WhatsApp options for receiving one-time password
Source: Bleeping Computer


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