UNC5221 / VerdantBamboo: Brickstorm, Plenet & AgentPSD — 18-Month Dwell via M365 SOCKS5 Proxy

DFIR deep-dive into UNC5221 (VerdantBamboo) — Brickstorm Go/Rust backdoors, Plenet .NET AOT, AgentPSD Python implant, Egnyte privilege escalation, and M365 SOCKS5 proxy bypass enabling 18-month network dwell.