Android malware steals payment card data using previously unseen technique

Newly discovered Android malware steals payment card data using an infected device’s NFC reader and relays it to attackers, a novel technique that effectively clones the card so it can be used at ATMs or point-of-sale terminals, security firm ESET said.

ESET researchers have named the malware NGate because it incorporates NFCGate, an open source tool for capturing, analyzing, or altering NFC traffic. Short for Near-Field Communication, NFC is a protocol that allows two devices to wirelessly communicate over short distances.

New Android attack scenario

“This is a new Android attack scenario, and it is the first time we have seen Android malware with this capability being used in the wild,” ESET researcher Lukas Stefanko said in a video demonstrating the discovery. “NGate malware can relay NFC data from a victim’s card through a compromised device to an attacker’s smartphone, which is then able to emulate the card and withdraw money from an ATM.”

The malware was installed through traditional phishing scenarios, such as the attacker messaging targets and tricking them into installing NGate from short-lived domains that impersonated the banks or official mobile banking apps available on Google Play. Masquerading as a legitimate app for a target’s bank, NGate prompts the user to enter the banking client ID, date of birth, and the PIN code corresponding to the card. The app goes on to ask the user to turn on NFC and to scan the card.

ESET said it discovered NGate being used against three Czech banks starting in November and identified six separate NGate apps circulating between then and March of this year. Some of the apps used in later months of the campaign came in the form of PWAs, short for Progressive Web Apps, which as reported Thursday can be installed on both Android and iOS devices even when settings (mandatory on iOS) prevent the installation of apps available from non-official sources.

The most likely reason the NGate campaign ended in March, ESET said, was the arrest by Czech police of a 22-year-old they said they caught wearing a mask while withdrawing money from ATMs in Prague. Investigators said the suspect had “devised a new way to con people out of money” using a scheme that sounds identical to the one involving NGate.

Stefanko and fellow ESET researcher Jakub Osmani explained how the attack worked:

The announcement by the Czech police revealed the attack scenario started with the attackers sending SMS messages to potential victims about a tax return, including a link to a phishing website impersonating banks. These links most likely led to malicious PWAs. Once the victim installed the app and inserted their credentials, the attacker gained access to the victim’s account. Then the attacker called the victim, pretending to be a bank employee. The victim was informed that their account had been compromised, likely due to the earlier text message. The attacker was actually telling the truth – the victim’s account was compromised, but this truth then led to another lie.

To “protect” their funds, the victim was requested to change their PIN and verify their banking card using a mobile app – NGate malware. A link to download NGate was sent via SMS. We suspect that within the NGate app, the victims would enter their old PIN to create a new one and place their card at the back of their smartphone to verify or apply the change.

Since the attacker already had access to the compromised account, they could change the withdrawal limits. If the NFC relay method didn’t work, they could simply transfer the funds to another account. However, using NGate makes it easier for the attacker to access the victim’s funds without leaving traces back to the attacker’s own bank account. A diagram of the attack sequence is shown in Figure 6.

The researchers said NGate or apps similar to it could be used in other scenarios, such as cloning some smart cards used for other purposes. The attack would work by copying the unique ID of the NFC tag, abbreviated as UID.

“During our testing, we successfully relayed the UID from a MIFARE Classic 1K tag, which is typically used for public transport tickets, ID badges, membership or student cards, and similar use cases,” the researchers wrote. “Using NFCGate, it’s possible to perform an NFC relay attack to read an NFC token in one location and, in real time, access premises in a different location by emulating its UID, as shown in Figure 7.”

The cloning could all occur in situations where the attacker has physical access to a card or is able to briefly read a card in unattended purses, wallets, backpacks, or smartphone cases holding cards. To perform and emulate such attacks requires the attacker to have a rooted and customized Android device. Phones that were infected by NGate didn’t have this requirement.