Recommended firewall ports to block

For those looking for a list of ports to block, the SANS Institute recommends at least blocking outbound traffic using the following ports:

MS RPC TCP, UDP Port 135.
NetBIOS/IP TCP, UDP Port 137-139.
SMB/IP TCP Port 445.
Trivial File Transfer Protocol (TFTP) UDP Port 69.
System log UDP Port 514.

What are the common ports not blocked?

Common port numbers that typically may be open include 21, 25, 80, 110, 139 and 8080. By default, these port numbers are usually active and open in most routers.

Should I close port 21?

This port should be blocked. Port 21 – Used by FTP to allow file transfers. Most hosts on your network are not intended to be FTP Servers - don't leave doors open that don't need to be open. Also consider using Secure FTP (SFTP) instead or other methods of encrypted file transfer instead of unencrypted FTP.

Is it OK to close port 80?

Closing port 80 doesn't reduce the risk to a person who accidentally visits your website via HTTP. In normal circumstances, that person would receive a redirect to HTTPS, and their subsequent traffic will be protected.

Should port 5357 be open?

Port 5357 Details. Used by Microsoft Network Discovery, should be filtered for public networks. Disabling Network Discovery for any public network profile should close the port unless it's being used by another potentially malicious service.

What is a typical firewall rule?

Rulesets for firewalls typically include the source address, the source port, the destination address, the destination port, and an indication of whether or not the traffic should be permitted. In the given ruleset for a firewall, for instance, the firewall itself is never directly accessible from the public network.

What ports are insecure?

Ports 80, 443, 8080 and 8443 (HTTP and HTTPS)

HTTP and HTTPS are the hottest protocols on the internet, so they're often targeted by attackers. They're especially vulnerable to cross-site scripting, SQL injections, cross-site request forgeries and DDoS attacks.

Which port is most secure?

Port 443 is the SSL function for HTTPS, used to transmit web pages securely through encryption techniques. Information that travels through port 443 is encrypted using SSL/TLS technology. This means that the connection is secure, and information is kept safe while in transit.

What are unsafe ports?

A port or berth will be unsafe if the ship is unable to reach the port safely. For example a port may be considered unsafe even if the ship suffers damage during its passage on a river or channel when approaching a port.

Is port 22 unsafe?

As such, Port 22 is subject to countless, unauthorized login attempts by hackers who are attempting to access unsecured servers. A highly effective deterrent is to simply turn off Port 22 and run the service on a seemingly random port above 1024 (and up to 65535).

Should I allow port 25?

Port 25 is still known as the standard SMTP port and it's used mostly for SMTP relay. However, if you're setting up your WordPress site or email client with SMTP, you usually do not want to use port 25 because most residential ISPs and cloud hosting providers block port 25.

Is port 20 and 21 secure?

For example, legacy FTP traffic that is transmitted over TCP port 21 is not a secure protocol. Files, credentials, and other information traversing FTP are transmitted in cleartext with no encryption. We often hear about the encryption used by the bad guys concerning ransomware.

Why should port 445 be closed?

We also recommend blocking port 445 on internal firewalls to segment your network – this will prevent internal spreading of the ransomware. Note that blocking TCP 445 will prevent file and printer sharing – if this is required for business, you may need to leave the port open on some internal firewalls.

Should port 22 be closed?

Is it safe to keep port 443 open?

HTTPS is secure and is on port 443, while HTTP is unsecured and available on port 80. Information that travels on the port 443 is encrypted using Secure Sockets Layer (SSL) or its new version, Transport Layer Security (TLS) and hence safer.

Why should port 135 be closed?

Hacker tools such as "epdump" (Endpoint Dump) can immediately identify every DCOM-related server/service running on the user''s hosting computer and match them up with known exploits against those services. Therefore, port 135 should not be exposed to the internet and must be blocked.

What is port 139 and 445 used for?

Ports 139 and 445 are used for 'NetBIOS' communication between two Windows 2000 hosts. In the case of port 445 an attacker may use this to perform NetBIOS attacks as it would on port 139. Impact: All NetBIOS attacks are possible on this host.

What is port 445 and 139?

What are Ports 139 and 445? SMB is a network file sharing protocol that requires an open port on a computer or server to communicate with other systems. SMB ports are generally port numbers 139 and 445. Port 139 is used by SMB dialects that communicate over NetBIOS.

Should I block UDP 443?

Blocking UDP going to 80 and 443 is sufficient. Chrome uses ephemeral ports, just like TCP, but the servers always use 80 and 443.

Is port 21 a vulnerability?

Port 20 and (mainly) port 21 are File Transfer Protocol (FTP) ports that let users send and receive files from servers. FTP is known for being outdated and insecure. As such, attackers frequently exploit it through: Brute-forcing passwords.

Should I close port 53?

You don't need to block port 53 on your router, but you do need to spot which one of your computers is generating this traffic. I would recommend downloading Avast or AVG (Free) together with Malwarebytes (also free) on all the PC's in your network and I'm positive you will find the culprit.