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

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19
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4answers
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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 ...
8
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2answers
2k views

ports blocked by firewall and not the server

I was asked this question at an interview and i wasn't sure about the answer. The question was "suppose you were checking the open ports on a particular webserver which was behind a firewall, how ...
7
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3answers
7k views

How to listen to all ports (UDP and TCP) or make them all appear open (linux)

I got an external Debian server. The problem is that my university campus doesn't allow connections to go outside when the port is different than TCP port 22, 80, 443, or UDP port 123. I tested them ...
7
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2answers
5k 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 ...
7
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1answer
374 views

different portscan tools give different results

I have different results as of my open TCP ports. When using nmap -sS 127.0.0.1, I get some 5 usual open ports, but when using osx built-in tool as stroke, I get those 5 ports plus 5 extra ports. How ...
7
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2answers
21k 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 ...
5
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2answers
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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 ...
4
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3answers
2k 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 ...
4
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2answers
596 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 ...
4
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5answers
946 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? ...
4
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2answers
959 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 ...
4
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4answers
1k views

How can I scan open ports without being traced back

I would like to scan open ports of a server. But as far as I know, when I try to scan the open ports with something like nmap in shell they would be able to trace me. Is there a way to secure this ...
4
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2answers
632 views

Detect what is running on an open port?

I have a wireless camera in my network. Running nmap on the camera, I discovered that the port 1010 is open but I could not find what it is used for. I looked in the administration pannel and did not ...
4
votes
4answers
6k 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 ...
3
votes
2answers
1k views

Is my ISP doing a port scan on my computer?

I have been logging incoming connections with iptables for a while and I have been observing the following popping up periodically: 11:45:10 my.com kernel: IPTABLES: SRC=220.255.XX.XXY ...
3
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2answers
2k views

If a port is closed how come you can still use it?

What does it actually mean for a port to be closed or stealthed? According to tests I've run all my ports (tested) are stealthed but clearly I can still use the internet. Also are the terms "blocked" ...
3
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2answers
786 views

Tools/methods helping to determine application/protocol serving specific port

I do blackbox testing of the server and figured out that there is a bunch of listening ports. I need to determine what services/protocols those ports are used for. What I've tried so far is to use ...
3
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3answers
2k views

Which of these ports are safe to leave open, which are not?

I just ran nMap against my IP address and got the following result: PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 23/tcp open telnet 80/tcp open http 443/tcp open https ...
3
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3answers
2k views

Is there is a way to lock my USB port over the device physically?

Is there is a way to lock my USB port over the device physically ? For example I am connecting the USB mouse and keyboard on an public computer but I do not want anyone to remove them physically. I ...
3
votes
1answer
823 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 ...
3
votes
2answers
106 views

Auditing Existing Socket Connection

Is there any way to interact with a program's socket traffic without installing Winpcap? I understand that the one listening program per port is a restriction regarding TCP/IP, but I guess I'm more ...
3
votes
1answer
70 views

Is it possible to find out what a remote user is trying to do connecting to a closed port?

From my iptables log, I can observe a particular remote IP address trying to connect to my server from port 80 to a private port number: Jul 09 01:24:41 example.com kernel: IPTABLES: IN=eth1 ...
3
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1answer
2k views

Is opening both TCP/UDP less secured than just TCP or UDP when needed and why?

If application needs opened port X UDP, or X TCP combination. Is there any potential risk by opening both UDP/TCP as I usually am not sure which one the application uses?
3
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2answers
346 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 ...
3
votes
1answer
1k 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 ...
2
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5answers
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Nmap reporting almost every port as open

I have noticed during some assesments when doing a TCP port scan, Nmap will report almost every port as open for a machine. Using for example nmap -sS -PN -T4 target -p0-65535, over 20,000 ports will ...
2
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3answers
178 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 ...
2
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2answers
2k views

how to identify p2p on network

Im trying to work out if the traffic in the below image is P2P file sharing? If you notice the source ports are all random but the time 17.24 from c.port 58338 runs for a good length maybe about 400 ...
2
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3answers
438 views

Why block network ports?

There was another good question here on why you should block outgoing traffic: Why block outgoing network traffic with a firewall? But I was hoping to get an answer on why it is a good idea to block ...
2
votes
2answers
4k 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 ...
2
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3answers
3k views

Is it really better to use port 80 or 443 for outgoing traffic in order to bypass user firewall?

I recently created a reverse connection shell in C#. I tested it with some computers and I noticed that some computers connected back correctly and I established connection with them but another ...
2
votes
1answer
531 views

Why are some ports reported as closed by nmap?

I was scanning a machine from inside the same LAN which is running and up to date Windows XP Home Edition which I suspect may be running some malware. The target machine has an up to date antivirus ...
2
votes
1answer
468 views

Unknown Service Identification

How can one identify a service running on a non-standard port? I'm not talking about services like webserver or FTP since nmap can do that without any problems. I'm talking about services that are not ...
2
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1answer
727 views

Analyzing wireshark results (openvpn)

I signed up to Mullvad for VPN service, and manually run OpenVPN from my Linux box. I rebooted my computer and make sure not to start any OpenVPN service. Yet when I did a Wireshark analysis I am ...
2
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2answers
7k views

Does portforwarding present a risk to anonymity?

AirVPN by default has all ports closed but allows port-forwarding. I think this is required for P2P. Is this a threat to anonymity (e.g. would the person at the other end of the P2P transmission know ...
2
votes
1answer
3k views

Detected Port Scanning Attack in ESET Smart Security

I receive a number of notifications from ESET Smart Security about Port Scanning attack. But I'm behind a router. But as far as I know, computers behind a router is not accessible from others (Please ...
2
votes
1answer
306 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 ...
2
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1answer
121 views

What does Msgsrvr and Scientia-ssdb do?

I'm having a task in a computer security class in school where I'm supposed to scan a host for open ports in order to find out what services is being run there. I have found out (among other things) ...
2
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0answers
48 views

Could you attack a port without knowing what service was listening? [duplicate]

A lot of discussion I see suggests that changing default ports for services is just "security by obscurity" and is easily defeated by scanning for open ports. My question is this, though, if the ...
2
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2answers
140 views

Hide logging server from DMZ

I have a server on my DMZ whichs relays syslog and OcsInventory messages to a server on a vlan for logging servers. In order to allow the packets to go through I must allow port 80 (OcsInventory) and ...
1
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4answers
249 views

What configuration will allow another computer in the internet to probe my computer's ports?

I've just tested my computer with Gibson's port scan test: The test results stated that my system is "uncommon". It also said that my computer deliberately chose not to return. But I did not do any ...
1
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2answers
2k views

SUN Remote Procedure Call Port 111 [closed]

I have found on my machine port 111 is open. This is listed as RPC. I understand there are possible attacks on this port. How can my machine be attacked if port 111 is open? How can I secure this ...
1
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3answers
690 views

Bibliography of attacks by port scanning techniques

I have to present a paper and make a presentation about the principal types of attacks by port scanning. What literature do you recommend to cover enough information about: types of attacks, port ...
1
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3answers
3k views

Why is system32/ntoskrnl.exe blocking port 80? [closed]

Today I've tried to start the Visual Studio Developer IIS as usual on Port 80, but this time it has quit with an error that port 80 is already in use. With netstat I've found out, that an application ...
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4answers
1k views

How to make nmap list an unfiltered port?

I have a host that is NAT'ed and I have opened a single port in my router so the host is reachable by the external world. I tested if it was reachable by running a service and connecting to it ...
1
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4answers
557 views

SYN scan victim sending back RST

I'm confused on the case of SYN scan and closed ports (the case of open ports makes sense). So, the attacker sends a ~40 byte SYN packet, a "closed port" would send a RST packet back to the attacker ...
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2answers
1k 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 ...
1
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3answers
882 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 ...
1
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3answers
84 views

Is forwarding a port(s) a security risk to all computers on the network or just one?

I know forwarding ports can add some security risk, but if I forward a port to a computer, say running linux, would it add a security risk to all computers on my network or just the one?
1
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2answers
148 views

What security does an ISP provide for its customers?

I've heard that ISPs provide some kind of protection; using NAT and firewalls, to prevent hackers from using tools such as nmap to attack customers from over the Internet. What other technologies are ...