Hackers exploit a vulnerability in Circuit-Switched Fallback system in 4G LTE networks to "steal" phone numbers of unsuspecting users. Image Credit: Supplied

Las Vegas: A group of Chinese researchers have demonstrated an “evil attack” called the “Ghost Telephonist” which allows hackers to take over phone numbers and gather call and message content.

The demonstration was made by the UnicornTeam researchers from 360 Technology, China’s leading security company, at the ongoing hacker summit Black Hat USA 2017 here, reports Xinhua News Agency.

In the team’s presentation, security researchers introduced one vulnerability in CSFB (Circuit Switched Fallback) in 4G LTE network.

In the CSFB procedure, the researchers found the authentication step is missing.

“Several exploitations can be made based on this vulnerability,” Unicorn Team wireless security researcher Huang Lin, told Xinhua.

“We have reported this vulnerability to the Global System for Mobile Communications Alliance (GSMA)”.

The team presented a scenario where one could reset a Google account password using a stolen mobile number.

After hijacking a user’s communication, researcher signed in the user’s Google Email and clicked “forget the password”. Since Google sends verification code to the victim’s mobile, attackers can intercept the SMS text, thereby resetting the account’s password.

The victim keeps online in 4G network unaware of the attack.

A lot of internet application accounts use verification SMS to reset the login password, which means an attacker can use a phone number to start password reset procedure then hijack the verification SMS.

According to the researchers, the attacker can also initiate a call or an SMS by impersonating the victim.

Furthermore, Telephonist Attack can obtain the victim’s phone number and then use the phone number to make an advanced attack.

The victim will not sense being attacked since no 4G or 2G fake base station is used and no cell re-selection. These attacks can randomly choose victims or target a given victim.

The research team proposed many countermeasures to operators and internet service provider as well. Researchers say now they are collaborating with operators and terminal manufactures to fix this vulnerability.