Open Ports: What They Are and Why You Need to Secure Them

Open ports enable services and applications to tướng perform their functions properly. However, certain ports may pose security risks to tướng your network. Read this article for a better understanding of why you should close risky, unused ports.

Ports allow communication between devices. Internet-facing services and applications essentially listen on ports for a connection from the outside to tướng vì thế their jobs. Without ports, communication between hosts over the mạng internet is not possible.

At times, the problem with ports is that those that are not supposed to tướng be open are inadvertently left exposed. An administrator at your company may have opened a port to tướng satisfy a request and forgotten all about it. A firewall configuration may have been automatically modified by an application, leaving some ports open without your knowledge.

It is often difficult to tướng assess and mitigate risks associated with an open port at any given time. Unfortunately, open ports provide a pathway for attackers to tướng exploit vulnerabilities in your system. Data breaches related to tướng open ports happen all the time.

At Intelligent Technical Solutions, this is an issue that we usually encounter from some of our clients. However, through an in-depth network assessment, we can discover open ports and services that potentially put our clients' networks at risk. We have been doing the same thing for our 368 clients and counting over the past 18 years.

In this article, we explain what open ports are and the security implications of having them open. We also discuss how they work and what you can vì thế to tướng secure them.

What Are Open Ports and How Do They Work?

Before we discuss why leaving some ports open is a security risk, let's first look into the specifics of what ports are.

The term port refers to tướng a communication endpoint or where all network communications start and kết thúc. A port identifies a specific process or service and is assigned a number depending on its specialized purpose.

In simpler terms, ports enable devices to tướng tell what to tướng vì thế with the data they receive over a similar network connection. For instance, emails are routed through a different port (port 25) kêu ca websites (port 80). A port currently in use cannot lập cập another service on it and will return an error message.

The transport layer of the Internet Protocol Suite, such as the Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), uses ports to tướng transmit and receive chunks of information, known as packets. An open port refers to tướng a TCP or UDP port number that is actively accepting packets. In other words, behind it is a system that is receiving communication. A closed port, on the other hand, rejects or ignores packets.

Some ports are reserved for specific protocols and are therefore required to tướng be open. In addition, ports are opened depending on your firewall configuration or operating system: what is open on one may be closed on another.

What Makes Open Ports Dangerous?

Open ports are not the issue per se. It's the applications and services listening on these ports.

Attackers can easily exploit weaknesses in the applications listening on a port. Hackers can take advantage of security vulnerabilities in older, unpatched software, weak credentials, and misconfigured services to tướng compromise a network.

Some ports are not intended to tướng be publicly exposed. For instance, the Server Message Block (SMB) protocol, which operates over TCP ports 139 and 445, is open by mặc định in Windows machines. It is meant only for tệp tin sharing, printer sharing, and remote administration.

Due to tướng numerous vulnerabilities in the earlier versions of the SMB protocol, it was exploited by threat actors in the highly publicized WannaCry ransomware attack. Computers infected with WannaCry scanned its network for devices accepting traffic on SMB ports to tướng connect to tướng them and spread the malware.

In addition, some ports are prone to tướng abuse. An example is Microsoft's remote desktop protocol (RDP), which allows a user to tướng access a remote host. According to tướng ITS Director of Operations Peter Swarowski, there are many attack vectors for bad guys trying to tướng get in through RDP.

"Some of them are unpatched systems with known vulnerabilities where they can bypass all authentication and get right into whatever is hosting RDP right away. Some of it is brute force, sánh if you have RDP exposed and you don't have the means for locking out accounts from several failed logins, hackers can get in that way," he explained.

How to tướng Secure Open Ports

Here's how you can secure your perimeter from the risks posed by vulnerable, unused, or commonly abused ports, according to tướng Swarowski:

1. Access ports using a secure virtual private network (VPN).

a máy tính xách tay using a secure virtual private network

If a business needed something lượt thích RDP, ITS would use an encrypted VPN connection to tướng access RDP instead of leaving it open to tướng the mạng internet. Users need to tướng connect to tướng the VPN first before they can gain access to tướng your RDP. That way, the VPN has to tướng be attacked and bypassed first before the attackers can then get into a vulnerable RDP connection.

2. Use multi-factor authentication.

a person doing online banking money transfer with multi-factor authentication

Having multi-factor authentication (MFA) helps significantly in securing an open service. Even if you have a credential leak or a brute-force attempt, the threat actors would be challenged with an additional code or authentication method that they would not be able to tướng bypass.

3. Implement network segmentation.

a secured segmented network

Network segmentation is a process by which a larger network is divided into smaller parts or subnets. If you have an open DVR (Digital Video Recorder) port for your camera system, another option for securing that is segmenting it off the rest of your network. Even if somebody gets into this DVR, they can't get into your server and your workstations or go after more critical data.

4. Scan network ports regularly.

a network scan for open ports

ITS runs a process that looks for unsafe open services, such as unencrypted, legacy ports on clients’ networks, sánh administrators can close them or replace them with a secure version. A weekly kiểm tra is initiated on every port on every managed device to tướng identify which ones are risky and need to tướng be restricted.

Manage Your Attack Surface

Your attack surface (i.e., the sum of all possible points that attackers can exploit) should be limited in size. Through a comprehensive network assessment, you can identify vulnerabilities in your physical and digital environments, including unused, exposed ports. Some open ports pose a danger to tướng your system and should be secured.

Keep your attack surface small with the help of ITS. ITS can assist you in ensuring the security of your infrastructure. Get in touch with our trương mục representatives today for your không tính tiền network assessment.