Executive Summary
Vidar Stealer, a prominent information stealer active since 2018, has undergone significant technical shifts in mid-2026 to enhance its evasion capabilities. Analysis by Zscaler ThreatLabz reveals that the malware has moved beyond simple XOR and standard ChaCha20 encryption to a sophisticated, multi-layered obfuscation scheme.
Starting with version 2.0, the malware utilizes a custom virtual machine (VM) executed via a bytecode interpreter and a custom stream cipher (ARX-based). These components are designed to be polymorphic at the build level; the opcodes, constants, substitution tables, and stream cipher transformations change with each new iteration. This approach specifically targets static signatures and automated sandboxes that rely on consistent patterns.
While the primary functionality remains information theft—targeting browser data, cryptocurrency wallets, and system grabbers—the increased complexity of its defensive measures signals a shift toward higher stealth for persistent credential harvesting operations.