StrandHogg 2.0 Emerges as 'Evil Twin' to Android Threat

A newly discovered Android vulnerability could enable attackers to access most applications on a target device if exploited, researchers report. StrandHogg 2.0, which affects most versions of Android, lets malicious apps pose as legitimate apps while hiding from victims.

Promon researchers named the vulnerability for its similarities to StrandHogg, a flaw the same organization found in late 2019. StrandHogg, named after an old Norse term for a Viking coastal-raiding tactic, could enable attackers to abuse legitimate apps to deliver malware so they can track users without their knowledge. At the time it was disclosed, the flaw had been exploited in the wild and affected all versions of Android up to Android 10.

StrandHogg 2.0 does not affect devices running Android 10, though researchers note many still run older versions. They cite Google data showing that as of April 2020, 91.8% of Android users are on version 9.0 or earlier: Pie (2018), Oreo (2017), Nougat (2016), Marshmallow (2015), Lollipop (2014), Kit Kat (2013), Jellybean (2012), and Ice Cream Sandwich (2011).

Researchers have not seen any malware using StrandHogg 2.0 in the wild. However, they call this flaw the "evil twin" of its predecessor because it enables broader attacks, is harder to detect, and lets attackers take advantage of nearly any application on a target smartphone. They believe StrandHogg's operators have learned and subsequently evolved their tactics. 

The first iteration of StrandHogg exploited the Android control setting TaskAffinity. This flaw takes advantage of Android's multitasking feature and leaves behind traceable pointers. The second version uses a technique that makes this threat harder for victims to detect.

StrandHogg 2.0 is executed through reflection, explains researcher John Høegh-Omdal in a blog post on the discovery. This means malicious applications can assume identities of legitimate apps while staying hidden. Once an attacker's app is downloaded, they can use StrandHogg 2.0 to access text messages and photos, steal login credentials, track GPS movements, make and record phone calls, and/or spy through the camera or microphone. 

The attack begins when a victim clicks the app icon of a legitimate app. But instead of viewing the legitimate app, the malware is displayed and can request permissions under the disguise of legitimate software. It may also appear as a malicious login page. The victim unknowingly grants permission or sends data to the attacker, who then is redirected to the legitimate app. With this level of access, an intruder can proceed to upload data from a victim's device.  

Like its "relatively less evil twin," StrandHogg 2.0 is "extremely dangerous" because it does not need root access or Android permissions to run, Høegh-Omdal wrote. It can hijack permissions of other apps with access to contacts or messages. Unlike its predecessor, which can only attack one app at a time, StrandHogg 2.0 can simultaneously attack multiple apps.

Høegh-Omdal anticipates malware exploiting StrandHogg 2.0 will be harder for antivirus and security scanners to detect. No external configuration is required to execute StrandHogg 2.0, giving attackers a chance to further obfuscate their operations. As he points out, code that comes from Google Play won't initially seem malicious to developers or security teams.

"Promon predicts that attackers will look to utilise both StrandHogg and StrandHogg 2.0 together because both vulnerabilities are uniquely positioned to attack devices in different ways, and doing so would ensure that the target area is as broad as possible," he wrote. Many mitigations that protect against StrandHogg don't work for StrandHogg 2.0, and vice versa.

StrandHogg 2.0 (CVE-2020-0096) has been classified as Critical by Google, which released a patch to Android ecosystem partners last month. A security fix for Android versions 8.0, 8.1, and 9.0 will be rolled out to the general public this month, Promon wrote in a blog post.

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