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Torii botnet –Not another Mirai variant

INTRODUCTION

2018 has been a year where the Mirai and QBot variants just keep coming. Any script kiddie now can use the Mirai source code, make a few changes, give it a new Japanese- sounding name, and then release it as a new botnet.

Over the past week, we have been observing a new malware strain, which we call Torii, that differs from Mirai and other botnets we know of, particularly in the advanced techniques it uses.

Unlike the aforementioned IoT botnets, this one tries to be more stealthy and persistent once the device is compromised, and itdoes not(yet) do the usual stuff a botnet does like DDOS, attacking all the devices connected to the internet, or, of course, mining cryptocurrencies. Instead, it comes with a quite rich set of features for exfiltration of (sensitive) information, modular architecture capable of fetching and executing other commands and executables and all of it via multiple layers of encrypted communication.

ANALYSIS OF THE INITIAL SHELL SCRIPT

The infection chain starts with a telnet attack on the weak credentials of targeted devices followed by execution of an initial shell script. This script looks quite different from typical scripts that IoT malware uses in that it is far more sophisticated.

The script initially tries to discover the architecture of the targeted device and then attempts to download the appropriate payload for that device.The list of architectures that Torii supports is quite impressive: including devices based on x86_64, x86, ARM, MIPS, Motorola 68k, SuperH, PPC - with various bit-width and endianness. This allows Torii to infect a wide range of devices running on these very common architectures.