Rootnik was an Android Trojan that repackaged legitimate apps and adapted the commercial Root Assistant rooting utility to gain root access on vulnerable older devices. Palo Alto Networks Unit 42’s December 2015 analysis found that Rootnik could then install persistent system apps, manipulate apps covertly, show intrusive ads and steal private device information. These are historical findings; they do not establish that Rootnik or its listed servers remain active today.
What was Rootnik?
Unit 42 described Rootnik as an Android Trojan that used a customized version of Root Assistant, a commercial one-click rooting utility. Rather than simply bundling an unchanged copy, the attackers modified and repurposed parts of the legitimate tool. Rootnik loaded the adapted rooting code dynamically from an encrypted DEX payload, according to Unit 42’s technical report.
Unit 42 reported observing more than 600 Rootnik samples in the wild in 2015. That was a count of samples examined at the time, not a count or estimate of infected devices.
Which Android devices did it target?
The report uses two related but distinct version descriptions. Its summary says at least five exploits could provide root access on devices running Android 4.3 and earlier. In its workflow description, Rootnik attempted rooting on devices running Android 4.4 or earlier only when conditions—including a configured geographic exclusion for China—were met. Neither statement means every device on those versions was vulnerable or successfully rooted.
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Unit 42 reported affected users in the United States, Malaysia, Thailand, Lebanon and Taiwan. It said the analyzed samples were configured not to attempt rooting in China. These are observations from the 2015 analysis, not a current map of infections.
How did Rootnik use Root Assistant to gain root?
After checking device conditions, Rootnik could attempt one or more exploits. The Root Assistant exploit table in Unit 42’s report named:
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| Exploit name | CVE listed in the report |
|---|---|
| sock_diag | CVE-2012-4221 |
| fb_mem | CVE-2013-2596 |
| msm_acdb | CVE-2013-2597 |
| put_user | CVE-2013-6282 |
| fj_hdcp | No CVE listed |
The report says the modified tool incorporated at least five exploits. Rootnik’s attempt depended on the device and its checks; the presence of an exploit in the toolkit alone does not show that every exploit worked on every target.
Unit 42 also examined Root Assistant versions 1.3.0 and 1.5.1. It characterized version 1.3.0 as comparatively easy to reverse engineer and said version 1.5.1 used a commercial packer. The report also described unauthenticated communication between the utility and its server and locally stored exploit executables. Those observations concern the versions analyzed in 2015, not necessarily current Root Assistant software.
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How did Rootnik spread?
Rootnik was found in trojanized copies of otherwise legitimate Android applications. Examples in the report included WiFi Analyzer, Open Camera, Infinite Loop, HD Camera, Windows Solitaire, ZUI Locker and Free Internet Austria. The report does not establish that the original, unmodified apps were malicious; it is the repackaged copies containing Rootnik that were the concern.
SecurityWeek’s contemporaneous December 7, 2015 coverage reported the incident as a Trojan modifying a legitimate root tool, consistent with Unit 42’s account.
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- MEMORIES MADE PICTURE PERFECT: Capture every angle in stunning clarity, from wide family photos to close-ups of friends, with the triple-lens camera on Galaxy A17 5G.
- NEED MORE STORAGE? WE HAVE YOU COVERED: With an improved 2TB of expandable storage, Galaxy A17 5G makes it easy to keep cherished photos, videos and important files readily accessible whenever you need them.³
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What could Rootnik do after gaining root?
After obtaining root access, Rootnik wrote four APKs to the system partition and rebooted. Unit 42 described their roles as follows:
- AndroidSettings.apk: promoted apps, including through intrusive full-screen advertisements.
- BluetoothProviders.apk and WifiProviders.apk: acted as remote-control components, enabling app installation and code downloads.
- VirusSecurityHunter.apk: collected private information.
The resulting capabilities included silently installing or removing apps and downloading executable files. The information the report says Rootnik stole included Wi-Fi details—such as passwords or keys and SSID/BSSID—location, MAC address and device ID. Writing components to the system partition helped the malware persist beyond an ordinary app installation.
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What did the 2015 report say about Rootnik’s infrastructure?
Unit 42 listed the domains applight[.]mobi, jaxfire[.]mobi, superflashlight[.]mobi and shenmeapp[.]info, and reported that the analyzed servers were active at the time of publication. The report noted earliest domain creation dates dating to February 2015. This historical statement is not evidence that those domains or servers are active now.
What can Android users do?
Unit 42’s 2015 recommendations were to install available Android security updates and avoid apps from unknown sources. The practical value of an update depends on whether the device maker or carrier still supplies patches for that specific model and software version.
- Check the device’s system update settings and install any available security updates.
- Prefer app sources you trust; be cautious with repackaged apps or downloads from unfamiliar sites.
- If a device is no longer receiving security updates, avoid relying on it for sensitive accounts or data.
The 2015 analysis cannot establish whether Rootnik remains prevalent today, whether any listed infrastructure still operates, or the patch status of a particular current device.
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