Evasive Malware Exploits Vulnerabilities in IoT Devices via DDoS Botnets

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Trellix Unveils Inner Workings of Evasive Masjesu Botnet

The cybersecurity firm Trellix has conducted an in-depth analysis of the Evasive Masjesu botnet, which has been wreaking havoc on IoT devices since at least 2023.

Botnet Targets IoT Devices for DDoS Attacks

The botnet has been operational since 2023, with its operator promoting its capabilities on Telegram channels targeting both Chinese and English-speaking users.
The operator’s Telegram channel boasts over 400 subscribers.
An examination of attack source countries reveals that the majority of affected devices are located in Vietnam, with additional compromises in Brazil, India, Iran, Kenya, and Ukraine.
This widespread distribution indicates a complex attack vector involving multiple Autonomous System Numbers (ASNs).

Masjesu’s Architectural Versatility

Masjesu can target various architectures, including:

i386
MIPS
ARM
SPARC
PPC
68K (Motorola 68000)
AMD64

The botnet spreads through vulnerabilities in:

D-Link routers
GPON routers
Huawei home gateways
MVPower DVRs
Netgear routers
UPnP services
Other IoT devices

According to Trellix, “Upon infection, the malware establishes a persistent connection to its command-and-control (C&C) domain, using a hardcoded TCP port for remote access.”

Persistance Mechanisms

To ensure persistence, the malware:

Creates a cron job to run a renamed executable every 15 minutes
Converts the process into a background daemon
Renames it to resemble a legitimate system component
Terminates commonly used processes, such as wget and curl
Restricts access to shared temporary folders

C&C Domains and Fallback IP Addresses

Masjesu employs multiple C&C domains and fallback IP addresses, along with a 60-second receive timeout on socket connections.

Upon receiving instructions from the C&C server, the botnet launches various types of DDoS attacks, including:

UDP
TCP
VSE
GRE
RDP
OSPF
ICMP
IGMP
TCP SYN
TCP ACK
TCP ACKPSH
HTTP floods

These attacks pose a significant threat to organizations reliant on online infrastructure, underscoring the importance of robust network security measures and regular updates to mitigate potential vulnerabilities.