Phishing attacks target mobile users via progressive web applications (PWA)

Cybercriminals use progressive web applications (PWA) to impersonate banking apps and steal credentials from mobile users.

ESET researchers detailed a phishing campaign against mobile users that uses Progressive Web Applications (PWAs). The threat actors used fake apps almost indistinguishable from real banking apps on both iOS and Android. The technique was first disclosed in Poland in July 2023 and later observed in Czechia and other countries like Hungary and Georgia.

The campaign used progressive web applications to impersonate banking apps and steal credentials from Android and iOS users.

A progressive web app (PWA) is an app that’s built using web platform technologies, but that provides a user experience like that of a platform-specific app.

The technique allows the installation of a phishing application from a third-party website without requiring the user to enable third-party app installations. For iOS users, this undermines the usual security assumptions of the “walled garden” approach. On Android, it can lead to the silent installation of an APK that appears to come from the Google Play store, further deceiving the user.

Phishing websites targeting iOS instruct victims to add a Progressive Web Application (PWA) to their home screens, while on Android, the PWA is installed after confirming custom pop-ups in the browser. The technique was first disclosed in Poland in July 2023 and later observed in Czechia by ESET researchers, with additional cases targeting banks in Hungary and Georgia.

“Insidiously, installing a PWA/WebAPK application does not warn the victim about installing a third-party application. On Android, these phishing WebAPKs even appear to have been installed from the Google Play store.” reads the report published by ESET. “Most of the observed applications targeted clients of Czech banks, but we also observed one phishing app that targeted a Hungarian bank and another targeting a Georgian bank.”

The analysis of the C2 servers and backend infrastructure used in these attacks, revealed that two different threat actors were operating the campaigns.

The phishing campaigns spotted by ESET targeted mobile users through three different URL delivery methods: automated voice calls, SMS messages, and social media malvertising. The automated calls warned users about outdated banking apps and sent a phishing URL via SMS after users followed prompts. SMS campaigns sent phishing links indiscriminately to Czech phone numbers. Social media malvertising involved ads on platforms like Instagram and Facebook, targeting specific demographics with calls to action. Upon clicking on these URLs, victims were redirected to phishing pages mimicking official app stores, such as Google Play or Apple Store.

Attackers attempt to trick victims into installing a fake “new version” of their banking app. Depending on the campaign, clicking the install/update button triggers the installation of a malicious app directly on the victim’s phone.

For Android users, this can be a WebAPK, while for both iOS and Android users, it may be a Progressive Web Application (PWA). The installation process doesn’t trigger browser warnings about unknown apps, exploiting Chrome’s WebAPK technology. iOS users are displayed a pop-up mimicking native prompts to add the phishing PWA to their home screen, without any warnings. Upon installing the apps, victims are asked to input their banking credentials, which are then sent to the C2 servers.

The experts noticed that the campaigns used two distinct C2 infrastructures, suggesting that two dinstict groups were operating the PWA/WebAPK phishing campaigns against Czech and other banks.

One group used a Telegram bot to log entered information into a Telegram group chat via the official API, while another group employed a traditional C2 server with an administrative panel, which is associated with an NGate Android malware campaign.

“We identified a novel method of phishing, combining well-established methods of social engineering along with the cross-platform technology of PWA applications. Cases targeting Android users, specifically via a copycat page of the targeted app’s Google Play store page and using WebAPK technology, were also found. Most of the known cases have been inside Czechia, with only two phishing applications appearing outside of this region (in Hungary and Georgia).” concludes the report published by ESET. “We expect more copycat applications to be created and distributed, since after installation it is difficult to separate the legitimate apps from the phishing ones.”

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Pierluigi Paganini

(SecurityAffairs – hacking, progressive web applications (PWA))