You might have encountered a pop-up advertisement that appears out of nowhere and surprise you that your mobile device has been infected with a dangerous virus and instructs you to install a security app to remove it immediately.
This malicious advertising web page automatically downloads an Android app installation (.apk) file to your device without requiring any approval.
Citing malware threats on your mobile device, attackers trick you to change your device's settings to allow installation of the third-party apps from stores other than Google Play Store and install the banking trojan app on your device.
Kaspersky researchers Mikhail Kuzin and Nikita Buchka discovered one such widespread malicious advertising campaign across Russian news sites and popular websites.
Since this August, the Trojan has infected over 318,000 Android devices across the world — thanks to Google AdSense advertisements that was being abused to spread malicious mobile banking trojan, dubbed Svpeng.
"When an APK file is broken down into pieces and handed over to the save function via Blob() class, there is no check for the type of the content being saved, so the browser saves the APK file without notifying the user," the duo explains in a blog post.Google has acknowledged the issue, blocked the malicious ads and planned to patch it, although it is unclear when the next Android Chrome version will be released.
However, if Google sticks to its six-week release cycle, users can expect an update on 3rd December 2016. So, malicious actors have over three weeks to exploit the flaw.
"[The] next time they (criminals) push their adverts on AdSense they may well choose to attack users in other countries; we have seen similar cases in the past; After all, what could be more convenient than exploiting the most popular advertising platform to download their malicious creations to hundreds of thousands of mobile devices?" the pair say.Even if the Google patch this issue with its next software update, attackers still have an evergreen technique to trick users into downloading malicious apps by exploiting vulnerabilities in popular websites.
For example, a recently disclosed XSS (Cross-Site Scripting) flaw, discovered by Indian security researcher Jitendra Jaiswal, on WhatsApp's official websites could allow attackers to trick users into downloading malware applications.
So, it is always a good idea to install apps from official Google Play Store as well as not to change default Android settings that prevent the installation of third-party apps.
So, the best recommendation for users is to think twice before installing any app (no matter how legitimate it looks) from untrusted sources or clicking on suspicious-looking links.