Tropidoor is a Windows backdoor delivered in DPRK-linked DeceptiveDevelopment campaigns through trojanized Bitbucket projects. A 64-bit downloader, observed as car.dll or img_layer_generate.dll, retrieved Tropidoor directly into memory while parallel components delivered BeaverTail and InvisibleFerret. Researchers found substantial code overlap with PostNapTea, a Lazarus RAT used against South Korean targets in 2022. The families share API hashing and Base64 plus AES-128 network encryption, although Tropidoor is implemented as a C DLL and used in social-engineering operations.