Skip to main content
Share Your Experience: Take the 2024 Developer Survey

Questions tagged [ports]

In computer networking a port is a software construct serving as a communications endpoint in a computer's host OS.

Filter by
Sorted by
Tagged with
38 votes
2 answers
50k views

What are the security implications of enabling UPnP in my home router?

I found port forwarding entries in home router that I haven't manually configured. Is that because of UPnP? Are applications simply able to tell the router to forward ports on their own? Are there ...
Kvass's user avatar
  • 507
31 votes
5 answers
13k views

How do you deal with massive port scans?

This morning I was looking through firewall logs and saw there were about 500 packets marked as port scan. The scanning range was from 1000-1200 5000-5200. The IP address is 85.25.217.47 which seems ...
PaddyKim's user avatar
  • 479
4 votes
3 answers
15k views

Setup of Kali Linux for reverse shell connections over the internet

I am running Kali Linux as a VM on my Windows machine which is NAT'd behind my company network, if I wish to pen test a website for a client and believe that a reverse shell is possible, what is a ...
SilverlightFox's user avatar
0 votes
4 answers
1k views

Running SSH on a different port vs adding the port number to a password

So, a pretty typical piece of advice is to run SSH on a high port number, thus decreasing the chances of it being attacked. The thing I have always wondered about though is that it seems more secure ...
David Mulder's user avatar
  • 1,368
32 votes
4 answers
22k views

Dangers of opening up a wide range of ports? (mosh)

Why do we generally configure firewalls to filter out all traffic that we don't specifically allow? Is this just an extra layer of security for defense-in-depth that buys us nothing if we are not ...
dr jimbob's user avatar
  • 39.4k
16 votes
2 answers
92k views

How do hackers take advantage of open ports as a vector for an attack?

It is widespread knowledge, and therefore a common practice, to close open ports on any machines connected to the internet. If for example, a typical program uses port xyz as it's communication ...
Franko's user avatar
  • 1,550
6 votes
4 answers
1k views

How can non-root intercept privileged loopback ports?

Please walk through how an attacker can intercept Chrome's connection to 127.0.0.1:999, as suggested by the warning below. This warning is consitently displayed across many versions of Chrome in many ...
personal_cloud's user avatar
6 votes
3 answers
13k views

Is QUIC (Quick UDP Internet Connections) safe to allow through firewall?

Our firewall currently blocks QUIC (UDP 443) traffic which seems to be enabled by default in Google Chrome. Is it safe to allow QUIC or should I wait until it is implemented in all the major browsers? ...
R. Blueryan's user avatar
4 votes
1 answer
6k views

Can closing port 80 lead to more security?

If a website is running on HTTPS only, is it reasonable to close port 80 of the web server and only leave port 443 open? Does this action provide more security for the website?
A.B.'s user avatar
  • 147
3 votes
2 answers
4k views

Why OpenVAS does not find all open ports compared to Nmap?

I recently launched a system discovery scan with OpenVAS to an IP from my net to compare its results to Nmap. As you can see in the image OpenVAS does not find all the ports Nmap does. Both scans ...
Jernimo Domnguez Fernndez-Nez's user avatar
2 votes
1 answer
199 views

Can a VPN provider or actors within its infrastructure access open ports on the client machine?

From my understanding of a VPN, it essentially creates a network between the two 'machines'. So if I have open ports (e.g. HTTP, SSH) on my client machine, those can be accessed by the VPN provider or ...
Wayne Shelley's user avatar
2 votes
3 answers
361 views

Closed Port security

I have what I think is a security IT question (I'm more of a programmer myself). Assuming I am running a dedicated machine (say a PC) for a single program, meaning that the only port visible and open ...
Legion's user avatar
  • 21
2 votes
1 answer
2k views

nmap not running as root shows unknown open ports for a fraction of a second

On a server running Ubuntu 14.04.2 I was doing some basic security auditing when I ran the command nmap -p -d 1-65535 as a non-root user. Interestingly it reported a few (1-5 at a time, average, ...
jtl999's user avatar
  • 123
1 vote
1 answer
3k views

What are the ports used by Online Email Accounts such as Yahoo Mail, Gmail, etc.?

Let us say that I send an email using Yahoo Mail or GMail. Can this email be intercepted using a packet sniffer? On which port does the email travel? HTTP, SMTP, POP3?
Matthew's user avatar
  • 631
1 vote
2 answers
5k views

How to check if a port can be accessed from the outside

I want to be sure that the firewall protecting the intranet is effectively rejecting/granting access to a port. I have no access to the firewall nor any other external machine. Is that possible at ...
estani's user avatar
  • 143
0 votes
2 answers
3k views

Vulnerability of the open port

I'm installing service on the cloud machine and I was wondering on port vulnerabilities for my customers. My service which lives on server A (often on a customer site) needs to access server B (...
John's user avatar
  • 11
15 votes
2 answers
8k views

What's the diff between blocking a port with a firewall and not starting a service on that port in the first place?

I was considering setting up a software firewall (pf) on my web server and did some research on them. Were I to do it, it'd involve basically blocking connections to all ports except 80, 443, and the ...
Garrett Albright's user avatar
13 votes
5 answers
36k views

Is there a nmap command to get the top # most common ports?

I understand nmap by default scans the top 1k 'most common' ports (-F reduces to 100) I understand it gets these 'most common' ports based on the nmap-services file, specifically the frequency (3rd ...
gregg's user avatar
  • 293
10 votes
2 answers
3k views

Is it good practice to manually lock down ports on each host

We have a strong perimeter firewall. Would it make sense to still use IPTables on each host to hard block any and all ports except for the ones that are needed (DNS, 80 for the web server, nagios ...
user974896's user avatar
9 votes
3 answers
2k views

Risk of running services on ports >1024

In a Reddit thread on securing SSH access to a Raspberry Pi, one commenter recommended running SSH on a non-standard port of 8123. Another commenter had this to say on the matter: Don't change ...
Cybergibbons's user avatar
  • 1,251
9 votes
6 answers
26k views

How to bypass Nmap blockage?

I rent a server, and my provider seems to be blocking nmap. Is there any other tools I could use to test my home network from the outside? Also, does blocking nmap on a network provide any security? ...
marcoo's user avatar
  • 894
9 votes
6 answers
43k views

Exploiting through a filtered port

I'm doing some pentesting against a machine the lecturer set up in the lab. NMAP shows port 445 to be filtered and Nessus confirms the ms08_067 vulnerability is present on that machine. I tried ...
Juicy's user avatar
  • 1,447
8 votes
4 answers
27k views

Router Ports open

What ports on my home router should be open, say if I'm only using it for browsing the internet. Right now these four are open, 23/tcp open telnet 53/tcp open domain 80/tcp open http 5000/...
Sean's user avatar
  • 411
8 votes
2 answers
23k views

Port scanning legal or not? [closed]

Is port scanning legal ? In which countries ? my option : I think port scanning is like a short-walk( or a long-walk) in the neighbourhood, just curious about neighbours are up to. I think that ...
Stelios Joseph Karras's user avatar
7 votes
1 answer
4k views

How does OS detection work in practice?

I was wondering how OS detection really works on Nmap. I know it is about to send different tcp probes to see how the target machine responds to them. But what kind of probes would distinguish a ...
Rox's user avatar
  • 801
7 votes
2 answers
5k views

How helpful is rkhunter?

I have a software firewall implemented on my server, and I have closed all unnecessary ports. I have strong passwords, and I validate user input on my website. With these things already in place, do ...
Hope4You's user avatar
  • 333
6 votes
5 answers
14k views

Can nmap take a list of ports to scan from a file?

Nmap can take a file containing a list of hosts to scan using the -iL flag. Is there similar functionality for a file containing a list of port numbers? I've scoured the man page, online docs at nmap....
user1330734's user avatar
6 votes
4 answers
2k views

Using non standard port numbers [duplicate]

Are there any security benefits to setting up the ports on your firewall to non-standard numbers? For example, using port 15 for the SQL service, or 8443 for https.
Terry's user avatar
  • 1,105
6 votes
5 answers
6k views

What are the best pratices to avoid my server being port scanned

The title probably says it all. I just want to know the best techniques to avoid having a port scanner detecting open ports on my server. I'm using a Linux distro as my OS (Ubuntu Server). Please, don'...
My kutje's user avatar
6 votes
2 answers
9k views

How should an outgoing connection white-list be created?

I see my previous question was closed as duplicate of Why block outgoing network traffic with a firewall?. The answers that everyone agree with mention the value of blocking outgoing connections (to ...
700 Software's user avatar
5 votes
2 answers
2k views

Hardening/Security considerations for torrent clients

I am running Synology's DSM torrent client on a NAS. As I have to (?) open and forward one UDP port for DHT and another one (UDP/TCP) for data transmission I am exposing myself to threats originating ...
Matthias Güntert's user avatar
4 votes
3 answers
9k views

How to figure out which open ports or services are insecure?

We have around one thousand machines on internet. We do port scanning with nmap, and find many ports open on these machines. Sometime we found administrative website using HTTP instead of HTTPS, we ...
user15580's user avatar
  • 777
4 votes
2 answers
2k views

Is is bad practice to use non-standard ports? (for example ssh from 22 to something different)

Background is that I am learning some technical stuff with the Enki App. In this case about security. The App states that it is a misuse of a port if I change for example the ssh port from 22 to ...
user avatar
3 votes
2 answers
1k views

How to practically detect current system net traffic?

I know that some viruses or trojans can install rootkits or bootkits to change system's normal behaviour; AFAIK for example filter queries for running processes or even hide active TCP ports. My ...
wiki's user avatar
  • 135
3 votes
2 answers
6k views

How to configure iptables for must open ports?

On my machine there are web services which can be accessed from any PC connected to the same network segment (WiFi for example). I want to use IPtables on the machine to prevent any web services from ...
sophist's user avatar
  • 51
2 votes
1 answer
1k views

How should I audit and monitor shared TCP ports in Windows?

Windows has a feature called .NET TCP Port Sharing which allows different .NET applications to share the same TCP/IP port. I would like to monitor the source and destination connections of each ...
makerofthings7's user avatar
0 votes
2 answers
15k views

Does having these ports open indicate any vulnerabilities?

I installed Ubuntu Gnome a couple of weeks ago along with a few packages and some software. When I scanned my localhost using Nmap, I got the following results. Are there any obvious vulnerabilities, ...
Dave Mn's user avatar
  • 119
0 votes
2 answers
203 views

Compromised server name and port number of a SQL Server DB Server

I would like to get an expert opinion on how dangerous is it to have the database server name and SQL server instance and port number compromised by accidentally exposing it in source code snippet ...
Paceman's user avatar
  • 101
0 votes
1 answer
495 views

Why should I use firewall to block ports with no running services? [duplicate]

A firewall is for blocking / limiting access to specific service / port. I know that it can be useful for allowing only certain IPs to a port (for example I don't want to have SSH open for the whole ...
tomsk's user avatar
  • 389
0 votes
2 answers
362 views

Only HTTP(S) port is open. Why do I need to worry about unpatched software?

Unpatched software poses no risk by themselves. They're only problematic when someone exploits it. How could malware get into my system if I do have unpatched software in general and I'm connected to ...
Pacerier's user avatar
  • 3,313