“The open ADB port plays the central role,” Plume researcher Gergely Eberhardt wrote in an email. “Combined with root access, a single pm install command can silently install any APK. This bypasses every one of Android’s default protections at once: signature verification, the “unknown sources” restriction, the permission-review dialog, and Play Protect scanning.”
Intruders at gates
The open ADB, along with the default presence of apps that have built-in proxy functionality, creates a dangerous mix that makes SuperBox a potent threat.
“This combination results in further infections involving additional residential proxies or IoT botnets, and the attackers are often the very customers of the primary proxy network,” Plume wrote. “The device owners get multiple bots they never asked for and are not aware of, all competing for the same hardware, and an IP address whose reputation now reflects whatever those bots utilize it for.”
Some of the proxy networking services that make use of SuperBox take measures to prevent their customers from accessing the local networks of SuperBox users. The recently disrupted Popanet, for instance, blocks local IP address ranges from outside the local network. Even then, Popanet users can access local IPs by specifying the special wildcard address 0.0.0.0, which Android then routes to the SuperBox IP 127.0.0.1. From that vantage point, proxy users can access the rest of the local network.
Monday’s post also reported that even the Popanet network was facilitating live exploit attempts. Plume wrote:
The internal-network protection issue that we described in the previous part isn’t just a theoretical concern. To confirm whether anyone is actually exploiting it, we ran a controlled experiment. We joined the Popanet network as a residential exit node and instructed the host that any connection coming through the tunnel targeting either port 5555 or 5858 (these are the most common ADB ports) would be redirected to our local honeypot. From the operator’s perspective, our node looked like any other regular residential endpoint serving customer traffic; from the inside, every attempt aimed to reach an ADB port through our node was captured.
We let the node run for over three weeks; over that period, the honeypot recorded 1,352 distinct attempts at reaching the ADB through the gap we identified earlier. All the attacks could be split into two families of loopback addresses targeting the local machine. The first is 0.0.0.0, supplied either as a raw address or embedded in a hostname via a wildcard DNS service such as nip.io. The second is 127.0.0.1, which the proxy blocked via isLoopbackAddress() as we explained earlier.
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