A new Android Trojan has hijacked more than 10,000 Facebook accounts by stealing session cookies, according to researchers at Zimperium. The malware uses social engineering to trick users into installing malicious apps from the Google Play Store and third-party app stores.

“The threat actors made use of several themes that users would find appealing such as free Netflix coupon codes, Google AdWords coupon codes, and voting for the best football (soccer) team or player,” Zimperium says. “Initially available in Google Play and third-party stores, the application tricked users into downloading and trusting the application with high-quality designs and social engineering.”

After the app is installed, the user is asked to log into their Facebook account. Notably, this attack uses Facebook’s legitimate single-sign-on portal rather than a credential phishing page.

“Contrary to popular belief that a phishing page is always at the forefront for compromising or hijacking an account, there are ways to hijack sessions even by logging into the original and legit domain,” the researchers explain. “This Trojan exploits one such technique known as JavaScript injection. Using this technique, the application opens the legit URL inside a WebView configured with the ability to inject JavaScript code and extracts all the necessary information such as cookies, user account details, location, and IP address by injecting malicious JS code.”

Zimperium also discovered that the attackers had left their command-and-control server exposed to the public internet, so anyone could access the stolen information and use it in further social engineering attacks.

“Malicious threat actors are leveraging common user misconceptions that logging into the right domain is always secure irrespective of the application used to log in,” the researchers write. “The targeted domains are popular social media platforms and this campaign has been exceptionally effective in harvesting social media session data of users from 144 countries. These accounts can be used as a botnet for different purposes: from boosting the popularity of pages/sites/products to spreading misinformation or political propaganda.”

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