Silver Fox

The Silver Fox threat group is conducting a phishing campaign targeting organizations in Russia and India with tax-themed lures. The attack chain utilizes a modified RustSL loader featuring geofencing and Phantom Persistence to deploy ValleyRAT. ValleyRAT subsequently downloads a novel Python-based backdoor called ABCDoor, which masquerades as a Tailscale VPN client and provides remote control and screen broadcasting capabilities.

2026-05-1310 minSekoia.iohigh

Silver Fox (also known as Void Arachne) is a China-based threat actor conducting dual-purpose campaigns in South Asia that blend financial cybercrime with APT-style espionage. Recent operations leverage tax-themed phishing to deliver evolving payloads, transitioning from the ValleyRAT backdoor to abused legitimate RMM tools, and most recently, a custom Python-based stealer disguised as a WhatsApp application.