312-50V13 · Question #88
What ports should be blocked on the firewall to prevent NetBIOS traffic from not coming through the firewall if your network is comprised of Windows NT, 2000, and XP?
The correct answer is B. 135 C. 139 E. 445. To prevent NetBIOS and associated Windows file-sharing traffic from traversing a firewall for older Windows systems (NT, 2000, XP), specific ports must be blocked.
Question
Options
- A110
- B135
- C139
- D161
- E445
- F1024
How the community answered
(38 responses)- B95% (36)
- D3% (1)
- F3% (1)
Why each option
To prevent NetBIOS and associated Windows file-sharing traffic from traversing a firewall for older Windows systems (NT, 2000, XP), specific ports must be blocked.
Port 110 is used by POP3 (Post Office Protocol version 3) for retrieving emails, unrelated to NetBIOS.
TCP/UDP port 135 is used by the RPC (Remote Procedure Call) Endpoint Mapper, which is heavily utilized by NetBIOS and other Windows services for inter-process communication.
TCP/UDP port 139 is the NetBIOS Session Service, historically used for NetBIOS over TCP/IP (NBT) for file and printer sharing.
Port 161 is used by SNMP (Simple Network Management Protocol) for network device management, unrelated to NetBIOS.
TCP/UDP port 445 is used by SMB over TCP/IP (Server Message Block), which provides direct file and printer sharing without needing the NetBIOS layer, prevalent in Windows 2000, XP, and later versions.
Port 1024 is often an ephemeral port or used by various non-standard services, but it is not a primary, well-known port for NetBIOS traffic to block specifically.
Concept tested: NetBIOS and SMB port numbers
Source: https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/service-overview-and-network-port-requirements
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