It's another day, and another backdoor Android exploit has been discovered. At the center of the discussion this time around is the Ragentek firmware used on a number of Android smartphones. Researchers from BitSight Technologies discovered two internet domains that were hardwired into the firmware. Until recently these domains were unregistered, so BitSight took it upon itself to register the domains to do a bit of testing. With BitSight now in possessions of the domains, it discovered that 2.8 million unique devices have sought to connect using the exploit. The firmware dangerously allows apps with escalated privileges to be installed, with BitSight writing, "The fact that the device reached out to defined head-ends immediately after initialization implies that the devices are affected by this issue out of the box, and were not subsequently compromised through other means, such as through a subsequent update." One BitSight researcher took to Twitter to describe the scope of the vulnerability:

This from one of the researchers who discovered the backdoor/rootkit preinstalled on 3 million Android phones. https://t.co/bOd8DKtzNY

— Dan Goodin (@dangoodin001) November 18, 2016

We're seeing lots of connections coming from all sorts of sectors, including healthcare, government and banking. Scary stuff.

The man-in-the-middle attack (MITM) that is possible with this type of exploit is compounded by the fact that Ragentek does not encrypt communications sent to and from affected Android devices. Even more damning is the fact that code-signing is also not employed, which would allow a remote attacker to execute malicious code with root privileges using the over-the-air update mechanism. Of the nearly 3 million Android devices that are affected, 55 different models are caught up in the mix.

The vulnerability has been found in multiple smartphone handsets from BLU Products, along with over a dozen devices from other vendors. The list of affected Android handsets includes:

BLU Studio G
BLU Studio G Plus
BLU Studio 6.0 HD
BLU Studio X
BLU Studio X Plus
BLU Studio C HD
Infinix Hot X507
Infinix Hot 2 X510
Infinix Zero X506
Infinix Zero 2 X509
DOOGEE Voyager 2 DG310
LEAGOO Lead 5
LEAGOO Lead 6
LEAGOO Lead 3i
LEAGOO Lead 2S
LEAGOO Alfa 6
IKU Colorful K45i
Beeline Pro 2
XOLO Cube 5.0