When your computer goes on the internet, it uses ports to help do its job. Both network administrators and hackers possess a keen interest in scanning these ports for weaknesses. However, what is a port, and why do individuals scan them?
Let's explore what port scanning is and how it affects you.
What Are Ports?
In networking, ports help a computer untangle all the data from the internet and ensure the data packets go to the right place. The data must go through the correct process, or things will go wrong.
Let's say you're watching a Netflix show while talking to someone on Skype. Both the data for your Netflix stream and the data from your call on Skype are coming down the same broadband pipe. When they arrive on your PC, they split off and go to separate processes.
By assigning your browser and Skype to different ports, a PC can keep track of which traffic goes where. Data can be simultaneously sent and received through these ports, preventing any confusion for the PC.
You'll often see port numbers lurking at the end of IP addresses after a colon. For instance, 192.168.1.180:53892 will communicate using port number 53892.
Typically, if a router or your PC isn't using a port, it'll prevent traffic from using it to help keep you safe from intruders. This is sometimes why you need to perform "port forwarding" to allow a program to connect to the internet.
The router suspects your program is up to no good, so it starts blocking the traffic from going through the port. By opening up the port, you're telling the router that you trust the program.
What Is Port Scanning?
It's vital to grasp that maintaining open ports on your router or PC could potentially leave them susceptible to port scanning attacks, which are maneuvers often executed by hackers.
Port scanning is a tactic that hackers use to understand how a target's device works. A hacker conducts a port scan attack to investigate all the ports associated with a device, distinguishing between filtered ports that are effectively closed off and those actively in use.
However, it's crucial to recognize that the knowledge gained from this process is just the tip of the iceberg for hackers. An open port can serve as an entry point for a hacker, providing them with a treasure trove of information about the targeted system.
A hacker can initiate a search for open ports and then engage in the process of reverse-engineering them to unveil the precise activities the device is engaged in.
The information acquired doesn't merely reveal the services the device is running; it also sheds light on the overall purpose of the device. By analyzing the accessible ports and the services linked with them, a hacker can deduce the device's role and, in a way, fashion a unique fingerprint that could serve as an exploitable element in a future attack.
This is why a vigilant network administrator can play a pivotal role in safeguarding their system. By actively performing a port scan on their network, administrators can proactively identify the very weaknesses that hackers could potentially leverage. This knowledge arms them to fortify their network against impending attacks while bolstering security effectively.
What Is a Port Scanner?
A port scanner can determine which ports on a system or network are receptive to incoming requests. Essentially, the port scanner sends requests to a range of port numbers and waits for responses, classifying each port based on the response it receives. Open ports will acknowledge the request, closed ports will reject it, and a filtered port won't send any response at all. When executed with malicious intent, this becomes a port scanning attack.
For instance, when initiating a network port scanning on localhost, the tool highlighted which ports were active, illustrating the significance of network security in mitigating the risks of port scan attacks.
Port Scanning vs. Network Scanning
Besides port scanning, network scanning also has an important place, and there are subtle differences between the two. Let's try to examine these differences under one table:
Criteria |
Port Scanning |
Network Scanning |
---|---|---|
Definition |
The process of probing specific ports on a target machine to determine their status (open, closed, or filtered). |
Identification of active devices within a network range. |
Purpose |
To identify vulnerabilities linked to open ports. |
To map out active devices on a network. |
Target |
A specific device or IP address. |
Multiple devices or an entire IP range. |
Outcome |
Discovery of open, closed, or filtered ports. |
Overview of active devices and their IP addresses in a network range. |
Relevance for Hackers |
To find potential entry points into a system. |
To get a comprehensive view of the network and find potential targets. |
While the port scanner searches for open, closed, or filtered ports for a specific address, network scanners aim to map the devices connected to a specific network. This is also an answer to why port scanning is useful for hackers. The hacker's primary purpose is to gain intelligence about the target system. Both port scanning and network scanning are very helpful to the hacker in this respect.
Different Types of Port Scans
Not all port scans are the same, and their variations cater to distinct needs and scenarios.
Let's begin by discussing the SYN Scan. Crafted for stealthiness, the SYN Scan, sometimes called the Half-Open Scan, initiates a TCP connection, one of the most common internet protocols, but doesn't finalize it. This method allows the scanner to determine an active port's status with minimal footprint.
For systems that rely on UDP, a protocol which, unlike TCP, doesn't require an end-to-end connection, the UDP Scan is paramount. It's different from its TCP counterparts because of its protocol nature and can often be slower and less reliable. However, it's invaluable when examining services like VoIP or DNS that primarily use UDP.
Diving deeper into the nuances of port scanning, you encounter methods like the FIN Scan. This approach takes advantage of particular behaviors in TCP, sending packets to check if a port is open but without standard flags.
How to Defend Yourself From Port Scanning
If you want to defend your home or work system from a port scan attack, the key isn't to stop someone from scanning your ports—that'll happen no matter what you do. The key is to stop the hacker from getting useful information from the scan.
Keep Your Firewall Updated and Running
Your firewall is your first line of defense against anything trying to abuse your system's ports. It's one of the many reasons you should use a firewall to browse the internet.
As such, keep your firewall running at all times and ensure it gets its security updates so it knows about current threats.
Reduce the Number of Internet-Connected Devices in Your Home
The 21st century has popularised the idea of connecting devices to the internet. It began with computers, laptops, and phones... but why stop there? Now, your security cameras, external hard drives, and fridge are all connected, day in and day out.
The problem is that each device needs a port through which to talk to the internet. The more ports you open up, the greater the risk that a hacker will find a flaw in one of them.
Likely, a hacker will only need one flaw to launch an attack, and it doesn't need to be a critical device, either. Do you think a hacker can launch an attack from a smart bulb? It turns out they can—and using them can put your network at risk.
The solution: reduce the number of internet-connected devices in your home. Devices like your PC and phone should be fine; however, if you have the choice between buying a smart gadget and a "dumb" equivalent, the latter will always be safer.
Double-Check for Unused Forwarded Ports
Sometimes, a program won't work unless you forward the port to your firewall and/or router. While having a forwarded port isn't ideal for security, it's sometimes a necessary evil so you can get used from your internet connection.
However, what about after you finish using that one game or piece of software that required a port forward? If you forget to delete the port forward, it'll sit there doing nothing productive and giving hackers a potential entry point into your network.
As such, it's a good idea to review your forwarded ports and erase the ones that aren't in use anymore. Double-check with any housemates or family members before closing a forwarded port you don't remember creating; it may still be important for them!
Keeping Your Ports Safe From Intruders
When a hacker performs a port scanner, they can use the information to find an open port and sneak into a system. Even if they can't, monitoring which ports are active can tell a potential intruder what a device does and the best way to attack it. Keep your firewalls updated, and don't buy too many smart devices to stay safe.
If you're worried about your router's overall security, check up on all the ways your router isn't as secure as you may think. There are plenty of ways you can tighten up security and stop hackers in their tracks.