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Mirai Variant Targets ARC CPU-Based Devices

A newly discovered variant of the Mirai Internet of Things (IoT) botnet is targeting devices with ARC (Argonaut RISC Core) embedded processors, researchers warn.

A newly discovered variant of the Mirai Internet of Things (IoT) botnet is targeting devices with ARC (Argonaut RISC Core) embedded processors, researchers warn.

Dubbed Okiru, the new malware variant appears to be different from the Satori botnet, although the latter was also called Okiru by its author. Security researchers analyzing the new threat have discovered multiple differences between the two Mirai versions, aside from the targeting of the ARC architecture.

Originally designed by ARC International, the ARC processors are 32-bit CPUs widely used in system on chip (SOC) devices for storage, home, mobile, automotive, and IoT applications. Each year, over 1.5 billion devices are shipped with ARC processors inside.

Mirai Okiru represents the very first known malware targeting ARC processors, independent security researcher Odisseus, who analyzed the threat, notes.

The botnet was discovered by @unixfreaxjp from, the security researcher who spotted the first Mirai variant in August 2016. In a post on reddit, the researcher explained that, although distributed denial of service (DDoS) is the main purpose of the last two Mirai versions, they are very different.

One of the characteristics that sets them apart is the configuration, which in Okiru is encrypted in two parts with telnet bombardment password encrypted. Satori doesn’t split it in two and doesn’t encrypt brute
default passwords either. Moreover, the new malware variant can use up to 114 credentials for telnet attack, while Satori uses a different and shorter database.

The researcher also explains that Okiru seems to lack the “TSource Engine Query” common Distributed “Reflective” (DRDoS) attack function via random UDP that Satori has. The two also have different infection follow up commands written in their configurations and show differences in usage of watchdog.

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Okiru was found to have four types of router attack exploit code hard coded in it, none of which is found in Satori. Furthermore, there are small embedded ELF Trojan downloaders in Satori, which are used to download other architecture binaries (these were coded differently compared to Okiru ones).

Last week, when the researchers first noticed Okiru’s attacks, the malware enjoyed low detection in VirusTotal. Thus, and because the new threat is targeting devices that haven’t been hit by malware previously, researchers expect an uptick in Mirai infections.

It is also clear that the actor behind the botnet is actively following reports on the malware. Within minutes after ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group member Pierluigi Paganini wrote about Okiru, the website was hit with a DDoS attack that lasted over an hour, Italy’s CERT-PA revealed (translated).

Related: Botnet’s Huawei Router Exploit Code Now Public

Related: Mirai Variant “Satori” Targets Huawei Routers

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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