Social engineering: Bitter relied on fictitious personas, posing as attractive young women, journalists or activists, across the internet to build trust with the people it targeted to trick them into clicking on malicious links or downloading malware. Rather than indiscriminately targeting people with phishing, this group typically invested time and effort in establishing connections with its targets through various channels, including email.
iOS application: Our most recent investigation found Bitter deploying a chat application for iOS that users could download via Apple’s Testflight service for developers to help them beta-test their new applications. This meant that hackers didn't need to rely on exploits to deliver custom malware to targets and could utilize official Apple services to distribute the app in an effort to make it appear more legitimate, as long as they convinced people to download Apple Testflight and tricked them into installing their chat application. We don’t have any visibility into whether this app contained malicious code and assess that it may have been used for further social engineering on an attacker-controlled chat medium. We reported our findings to Apple.
Android malware: We found Bitter using a new custom Android malware family we named Dracarys. Notably, it used accessibility services, a feature in the Android operating system to assist users with disabilities, to automatically click through and grant the app certain permissions without the user having to do it. Bitter injected Dracarys into trojanized (non-official) versions of YouTube, Signal, Telegram, WhatsApp, and custom chat applications capable of accessing call logs, contacts, files, text messages, geolocation, device information, taking photos, enabling microphone, and installing apps. While the malware functionality is fairly standard, as of this writing, malware and its supporting infrastructure has not been detected by existing public anti-virus systems. It shows that Bitter has managed to reimplement common malicious functionality in a way that went undetected by the security community for some time.