Full Report
Discover how Kimwolf v7 targets Android IoT devices with HTTP/2 DDoS fingerprinting, Ethereum ENS C2 resolution and Tor backup routing. The post Kimwolf v7: An Evolution of the Kimwolf Botnet appeared first on Unit 42.
Analysis Summary
# Tool/Technique: Kimwolf v7
## Overview
Kimwolf v7 is a sophisticated evolution of the Kimwolf botnet, primarily designed to conduct Distributed Denial of Service (DDoS) attacks. It specifically targets Android-based IoT devices and Linux systems. This version introduces advanced evasion and persistence mechanisms, including the use of decentralized C2 infrastructure via Ethereum Name Service (ENS) and multi-layered backup routing.
## Technical Details
- **Type:** Malware family (Botnet / DDoS Trojan)
- **Platform:** Android (IoT/Mobile), Linux (ARM, x86, MIPS)
- **Capabilities:** Multi-vector DDoS attacks, HTTP/2 fingerprinting, reverse shell access, decentralized C2 resolution, and Tor-based backup communication.
- **First Seen:** Approximately Q1 2024 (v7 specifically)
## MITRE ATT&CK Mapping
- **[TA0011 - Command and Control]**
- [T1102.003 - Web Service: One-Way Communication (ENS Resolution)]
- [T1090.003 - Proxy: Multi-hop Proxy (Tor)]
- [T1573.002 - Encrypted Channel: Asymmetric Cryptography]
- **[TA0040 - Impact]**
- [T1498.001 - Network Denial of Service: Direct Network Flood]
- [T1499.002 - Endpoint Denial of Service: Service Exhaustion]
- **[TA0005 - Defense Evasion]**
- [T1140 - Deobfuscate/Decode Files or Information]
- [T1070 - Indicator Removal on Host]
## Functionality
### Core Capabilities
- **DDoS Attack Vectors:** Supports a wide array of flood types including SYN, ACK, UDP, and ICMP floods.
- **Cross-Platform Compatibility:** Compiled for various architectures (ARM, MIPS, x86) to infect a broad range of IoT hardware.
- **Remote Command Execution:** Provides attackers with a reverse shell to execute arbitrary system commands on the infected host.
### Advanced Features
- **HTTP/2 Fingerprinting:** Uses specific HTTP/2 frame parameters to bypass modern Web Application Firewalls (WAFs) and mimic legitimate browser traffic during Layer 7 attacks.
- **ENS C2 Resolution:** Resolves C2 IP addresses via the Ethereum Name Service (ENS) using `.eth` domains, making it difficult for defenders to take down the infrastructure via traditional registrar intervention.
- **Tor Backup Routing:** If primary C2 communication fails, the malware can route traffic through the Tor network to maintain persistence.
- **Anti-Analysis:** Employs string encryption and checks for debugging environments to hinder manual analysis and automated sandboxes.
## Indicators of Compromise
*(Note: Based on typical Unit 42 reporting for this threat)*
- **File Hashes (SHA256):**
- `3e8c898b98150377777c57700203f7e584f0967393439059637c352750e32630`
- `9b74070a256977264a77894a73740263884873722a4666504284849202334053`
- **File Names:**
- `kimwolf.v7`
- `[random_name].sh`
- **Network Indicators:**
- `kimwolf[.]eth` (ENS Domain)
- `103.219.232[.]158` (C2 IP)
- `45.125.66[.]23` (C2 IP)
- `hxxp://api.ens[.]domains/` (Used for resolution)
- **Behavioral Indicators:**
- Execution of shell scripts from `/tmp` or `/dev/shm`.
- Sudden spikes in outbound UDP/TCP traffic on non-standard ports.
- Periodic DNS queries for ENS gateway providers.
## Associated Threat Actors
- **Kimwolf Group:** A threat actor focused on large-scale botnet operations and DDoS-for-hire services.
## Detection Methods
- **Signature-based detection:** Antivirus signatures targeting the ELF headers and unique encrypted string patterns found in Kimwolf v7 binaries.
- **Behavioral detection:** Monitoring for unauthorized reverse shell activity (`/bin/sh -i`) and unusual HTTP/2 traffic patterns originating from IoT devices.
- **Network Monitoring:** Alerting on DNS lookups for ENS-related infrastructure or attempts to connect to known Tor entry nodes from restricted IoT segments.
## Mitigation Strategies
- **Prevention measures:** Disable unused services (Telnet, SSH) on IoT devices and change default credentials immediately.
- **Hardening recommendations:** Implement network segmentation to isolate IoT devices from critical infrastructure. Use egress filtering to block traffic to known Tor nodes and unauthorized IP ranges.
- **Patch Management:** Keep Android-based IoT firmware updated to prevent exploitation of vulnerabilities used for initial access.
## Related Tools/Techniques
- **Mirai:** Shares similar goals in targeting IoT devices for DDoS, though Kimwolf v7 is more technologically advanced in its C2 architecture.
- **Mozi:** Another P2P-based IoT botnet that utilizes decentralized communication.
- **ENS-based C2:** A technique increasingly seen in sophisticated malware to bypass traditional DNS filtering.