Android Devices Targeted by New Monero-Mining Botnet

A new botnet appeared over the weekend, and it's targeting Android devices by scanning for open debug ports so it can infect victims with malware that mines the Monero cryptocurrency.

The botnet came to life on Saturday, February 3, and is targeting port 5555, which on devices running the Android OS is the port used by the operating system's native Android Debug Bridge (ADB), a debugging interface that grants access to some of the operating system's most sensitive features.

Only devices running the Android OS have been infected until now, such as smartphones, smart TVs, and TV top boxes, according to security researchers from Qihoo 360's Network Security Research Lab [Netlab] division, the ones who discovered the botnet, which the named ADB.miner.

The botnet has been extremely aggressive and has grown each day, exhibiting a worm-like behavior, with infected devices scanning the Internet for other victims.

"The number of scan [sources] has doubled every 12 [hours]," said Yiming Gong, Director of the Network Security Research Lab at Qihoo 360. "We will see how big this botnet gets."

Currently, Netlab has detected ADB.miner scans coming from nearly 7,400 unique IP addresses, based on public data collected by Netlab's Scanmon system.

Scanning for this port has been so widespread that port 5555 shot to the #4 spot in Netlab's most scanned ports. Previously, it wasn't even in the top 10.

Most IP addresses scanning for other devices (meaning they are already infected) are located in China (~40%) and South Korea (~30%). Yiming told Bleeping Computer that the botnet has mostly infected "TV-related" devices, rather than smartphones.

ADB.miner also marks the first time an Android malware strain has borrowed code from Mirai, a strain of Linux-based malware that has previously targeted only networking and IoT devices. Netlab says ADB.miner used some of Mirai's port scanning code.

Researchers didn't provide any details regarding the ADB vulnerability attackers are using to take over devices but clarified that they don't think the bug is specific to any particular vendor. This most likely means the bug affects the core of the Android ADB component itself.

By default, all Android OS instances ship out with the ADB port disabled. The devices taken over by this botnet are devices where vendors or users intervened and enabled port 5555 by hand.

An analysis of the ADB.miner malware source code revealed that crooks are mining Monero using the same Monero wallet address on two different mining pools. At the time of writing, attackers didn't cash out any of their mined Monero.