.rar files from third-party sites are common vectors for malware. Always run a scan before extracting.
Searching for "RimWorld.v1.4.3549.rar" typically points toward archived versions of the game found on file-sharing or pirate sites. If you are looking for a "good piece" regarding this specific version, here is the context on why it matters and what you should know. What is Version 1.4.3549? RimWorld.v1.4.3549.rar
The core of the Biotech DLC, allowing for hereditary traits and xenohumans. Why use a .rar file of an old version? RimWorld.v1.4.3549.rar
This specific build was part of the era of RimWorld . Released in late 2022, version 1.4 was one of the most transformative updates in the game's history, introducing: RimWorld.v1.4.3549.rar