An air-gapped sandbox is a virtual machine or a physical device that is isolated from any network connection.
This allows the analyst to safely execute the malware binaries and observe their behavior without risking any communication with the attackers or any damage to other systems. Uploading the binary to an air-gapped sandbox is the best option to gather intelligence without disclosing information to the attackers12 References:
1: Dynamic Analysis of a Windows Malicious Self-Propagating Binary 2: GitHub - mikesiko/PracticalMalwareAnalysis-Labs: Binaries for the book Practical Malware Analysis