What is a NetBios Vulnerability, what is the risk and how can you mitigate that risk? - Skyway West (2024)

FAQs

What is NetBIOS vulnerability? ›

The NetBIOS Name Server (NBNS) protocol does not perform authentication, which allows remote attackers to cause a denial of service by sending a spoofed Name Conflict or Name Release datagram, aka the "NetBIOS Name Server Protocol Spoofing" vulnerability.

Impact: If NetBIOS is enabled and open to the outside, attackers may try to reach shared directories and files. This also gives sensitive information to the attacker such as the computer name, domain, or workgroup.

NetBIOS is an abbreviation of Network Basic Input/Output System. The primary purpose of NetBIOS is to allow applications on separate computers to communicate and establish sessions to access shared resources, such as files and printers, and to find each other over a local area network (LAN).

Security Concerns with NetBIOS

Since NBT is an unauthenticated protocol, it's susceptible to poisoning attacks. This is when an attacker on the network impersonates, or 'spoofs,' another resource's identity and misdirects the victim's traffic.

Step 1: Open control panel Step 2: Navigate to programs and features. Step 3: Click on "Turn Windows features on or off. Step 4: Disable "NetBios over TCP/IP"Step 5 : Click ok.

Disabling NETBIOS on Windows™ servers

In most instances, some improvement in performance will result if you disable NETBIOS on the Windows™ server where you are installing the Conversion component. If using CIFS (SMB) to access any shared storage from this server, DO NOT disable NETBIOS.

NetBIOS (Network Basic Input/Output System) is a network service that enables applications on different computers to communicate with each other across a local area network (LAN).

NetBIOS domain name: Typically, the NetBIOS domain name is the subdomain of the DNS domain name. For example, if the DNS domain name is contoso.com, the NetBIOS domain name is contoso. If the DNS domain name is corp.contoso.com, the NetBIOS domain name is corp.

Both your Active Directory domain FQDN and NetBIOS can be confirmed using simple command prompt commands. Type nbtstat -n and it will display some information. Under Name will be several entries: the NetBIOS will be one of the Group type.

There should be no need for NetBIOS as long as either the DNS suffixes are set correctly or FQDNs are used – I've disabled it for years and am happy the results. Consider only allowing RPC from IT workstations and network management servers.

Should NetBIOS be blocked? ›

How can you mitigate the risk? The most effective mitigation is to not use NetBIOS (Windows file and printer shares) at all, but many organizations rely on these services. The next best approach is to block NetBIOS traffic to/from the Internet, or limit its use to specific IP addresses, using firewall rules.

Port 137 is utilized by NetBIOS Name service. Enabling NetBIOS services provide access to shared resources like files and printers not only to your network computers but also to anyone across the internet. Therefore it is advisable to block port 137 in the Firewall.

The NetBIOS Name Server (NBNS) protocol does not perform authentication, which allows remote attackers to cause a denial of service by sending a spoofed Name Conflict or Name Release datagram, aka the "NetBIOS Name Server Protocol Spoofing" vulnerability.

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "MSS: (NoNameReleaseOnDemand) Allow the computer to ignore NetBIOS name release requests except from WINS servers" to "Enabled".

A denial of service vulnerability exists when Microsoft Windows improperly handles NetBIOS packets. An attacker who successfully exploits this vulnerability could cause a target computer to become completely unresponsive. To learn more about the vulnerability, go to CVE-2017-0174.

When making outbound connections to servers, SMB 1 and NetBIOS are enabled by default in macOS to improve compatibility with third-party products. macOS will attempt to use the later versions of SMB, as well as DNS and port 445, with failover to port 139 and SMB 1 as needed.