port3 (VM outgoing interface)
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port3 is reserved for outgoing communication triggered by the execution of the files under analysis.
FortiSandbox uses port3 to allow scanned files to access the Internet. The Internet visiting behavior is an important factor to determine if a file is malicious. As malicious files are infectious, ensure that the connection for port3 is isolated but can also access the Internet. Do not allow this connection to belong to or be able to access any internal subnet that needs to be protected. Fortinet recommends placing this interface on an isolated network behind a firewall.
FortiSandbox VM accesses external networks through port3. Configure the next hop gateway and DNS settings in Scan Policy and Object > General Settings > Allow Virtual Machines to access external network through outgoing port3. This allows files running inside VMs to access the external network. One special type of outgoing communication from a guest VM is to connect to the Microsoft activation server to activate the Windows Sandbox VM product keys. Office licenses are verified through VM machines so internet access via port3 is required to contact Microsoft for license activation.
If the VM cannot access the outside network, a simulated network (SIMNET) starts by default. SIMNET provides responses to popular network services like http where some malware is expected. If the VM internet access is down, the SIMNET status is displayed beside the down icon. Click that icon to go to the VM network configuration page.
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SIMNET is not a real internet. This can affect catch rate. Do not use an IP address from the production IP pool for the IP assignment on port3 because it might get put on the blocklist.
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