The files for .NET 3.5 are actually included on your Windows installation USB or ISO file. You don't need to download a separate .exe if you have the media.
The Complete Guide to .NET Framework 3.5 Offline Installer (64-bit) net framework 3.5 offline installer 64 bit
3.5 SP1 (includes 2.0 and 3.0) File size: ~231 MB (full offline installer) Target OS: Windows 7, 8, 10, 11 (64-bit) Official source: Microsoft Download Center The files for
But here is the catch: That tiny file is a trojan horse. It doesn't actually contain the framework. When you run it, it reaches out to Microsoft’s servers, checks what your specific Windows version needs, and then downloads the necessary files on the fly. it reaches out to Microsoft’s servers
Method 1: Using Windows Installation Media (The "True" Offline Method)