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

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Opening outgoing ports on dedicated machine [migrated]

I have a website where I have been working with another person on a game server listing site. It queries the game servers and shows information etc. Anyway upon talking to the creator of the script he ...
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40 views

How do I check for inside-out open port? [closed]

I'm inside a corporate network and I want to assess which ports are open for outbound connection. There are such tools that do this test? I remember that years ago I used a website which performed ...
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24 views

How to know who is knocking on the door (or port)? [migrated]

Having a Linux server with only one port open 22, how can I log attempts to connect to any other port? They are closed, but I'd still want to know.
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1answer
38 views

Source port and destination port [closed]

Just fiddling with wireshark and telegram as part of some learning exercise on security. I realised that the source port for the telegram app is 58939 and the destination port would be 443. Why is ...
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1answer
91 views

Firewalk through a Firewall on our subnet

Having trouble firewalking. I am trying to determine all the open ports on my firewall/gateway. Here is my lab network diagram: (Skip to the bottom of the following explanation for a direct list of ...
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2answers
106 views

Opening port 53 on server Risks?

I looked about but couldn't find a similar enough question. I have some remote servers positioned on clients networks, which provide various services (raspberry pi) - and their firewall config is as ...
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1answer
73 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, ...
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2answers
732 views

Why would a stealth scan attract more attention than a connect scan?

I'm reading an Information Security book and am faced with the question: Why may nmap stealth scans(SYN) attract more attention than simple connect scans(TCP connect())? Why might it be?
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0answers
93 views

open ports on a netgear N-150 router; disable SPI firewall? [closed]

How do I open all ports? At least internally, for LAN traffic from 192.168.1.x to 192.168.1.x I want all ports open. Even if it creates a security problem. thufir@doge:~$ thufir@doge:~$ nmap -p ...
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2answers
83 views

Mitigating DDoS With Command of Ports

Is there any type of DDoS where closing or taking full control of all port capabilities would be useful in mitigation of an attack?
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350 views

Security risk of opening port 111 (rpcbind)?

As far as I understood rpcbind is used for listing active services, and telling the requesting client where to send the RPC request. If a host listens on port 111, one can use rpcinfo to get program ...
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1answer
94 views

What is the fastest way to scan all ports of a single machine

I am doing some research and I need a very quick way to scan for open ports on a single machine. To provide some context, I know that my machine will have a port open waiting for UDP packets for about ...
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1answer
72 views

How am I affected by malware? Malware transferred from service provider's base station or just port scan? [closed]

I need a malware expert here. I am being targeted by advanced hackers over the 4.5 years. So this is my situation: 1) My new phone: I just bought a new phone, with SIM card and mobile internet plan ...
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1answer
6k views

GHOST: which services are vulnerable, ssh, web server?

GHOST (CVE-2015-0235) just popped up. GHOST bug: is there a simple way to test if my system is secure? deals with how to find out if your system is vulnerable. exim is mentioned specifically. ...
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2answers
872 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 ...
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4answers
409 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 ...
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1answer
99 views

Understanding nmap output / author explanation …(Scapy)

I just read this example and explanation (below) in the OReilly book Security Power Tools (2007) in section 6.3 that is written by the creator of Scapy, Philippe Biondi. I think the example is very ...
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1answer
274 views

Firewall and Torrent

I use my university internet network and all incoming connection is blocked on every port.(they use netasq firewall) They have no other restrictions which stops me from using a torrent client. Using ...
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1answer
96 views

Why is nmap that slow on my system (ubuntu 14.04)?

I just started to learn something about portscanning with nmap. when i try to run an a nullscan or any other type on a virtual machine (win7 no firewall) the scan needs a lot of time to perform: ...
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4answers
5k views

Is there any meaning in only allowing port 80 and 443 today?

It's become standard fare for security minded organisations to block everything other than 80 and 443. As a result, more and more applications (other than web browsers) are learning to use these ports ...
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2answers
103 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 ...
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2answers
293 views

Which all ports are in danger and needs to be closed with immediate attention?

This is the nmap scan results on my server (used for email and web serving) from a remote scan. Which all ports are in danger and why? PORT STATE SERVICE 21/tcp open ftp 25/tcp open ...
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2answers
370 views

How to force nmap to check all the ports?

I heard that nmap scans for only 1000 most common ports while we do server scan. Is it possible to force nmap to check all the ports for scanning? If yes,How?
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2answers
95 views

What is the safest way to ssh to a machine behind a router?

I am thinking about forwarding port 22, to 22 on the machine behind router, but is it safe? Anyone can try to connect to my public IP on port 22 and then indefinitely try to guess user and password. ...
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3answers
67 views

What Mechanisms Keep Network Processes (and Applications) Sandboxed

This question stems from my other question, sorry if it is too similar. Now I would like to know what mechanism is used to sandbox network processes and (if relevant) individual programs, if at all? ...
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1answer
135 views

Telnet Open, is this an exploit? [closed]

I am pentesting a server, and it appears my ports are open for telnet. Upon accessing telnet, if I type "help" I only get these commands: telnet> help Commands may be abbreviated. Commands are: ...
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1answer
123 views

Are these port secured on my AP?

I'm doing a project for my high-school and I'm trying to get the best security for my network. I've made almost everything in my access-point configuration and I have only 3 tcp/ports open on my AP: ...
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2answers
159 views

Protecting against GCHQ port scans: How does TCP stealth work?

Today I read the first time about a draft of TCP Stealth which should serve as a protection against GCHQ and NSA vulnerability scanning(Source: https://en.wikipedia.org/wiki/TCP_Stealth): The ...
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2answers
472 views

How nmap guesses the operating system?

nmap has the capability to guess the operating system with the option -O. I was highly surprised that it can find the correct kernel or service pack. * How nmap guesses the operating system? * What ...
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2answers
88 views

Impossible to make connections through closed ports?

If you have closed all your ports on your internet protocol, you cannot make a connection to that internet protocol. So how do attackers (DoS or any other means that need a connection) make a ...
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1answer
175 views

Internal IP addresses allowed access to all DMZ hosts

Hi basically I'm doing a vulnerability assessment for at the moment. The setup includes a DMZ with a single firewall and an internal network (3 legged network model employing a single DMZ) but on the ...
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2answers
225 views

Does Nmap requires a closed TCP port to do OS fingerprinting?

I was checking the security of a server by running Nmap. Last time it gives me the following results, indicating that OS could not be fingerprinted: PORT STATE SERVICE VERSION 21/tcp ...
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2answers
168 views

How common is port-knocking? [closed]

Today I read about port-knocking for the first time. It has been a pretty known concept for more than ten years, but I don't know anybody who uses it for their servers. How common is the usage of ...
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149 views

OSSEC, what is it telling me about port changes?

I've been diving into OSSEC for the last couple of months, but I feel unclear on one of it's alerts. I've provided the alert below. The main difference I see in previous output and current output is ...
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1answer
113 views

Detecting port scans in OSX kernel

Is it possible to detect port scans on OSX at the kernel level? I would like to write a kext that detects the ip addresses of systems scanning my computers ports. How exactly does a stealth scan ...
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1answer
89 views

Web browser initiating connection on non-standard ports. Should it be blocked?

I am doing some egress monitoring on my computer. Once in every few days, I would find some strange connections being logged, which I believe is initiated by the web browser through a related but not ...
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1answer
182 views

How to check whether firewall allows traffic on specific port but not listening on the port [closed]

I have client / server and there is a firewall between them.The server is listening on a port and I want to check if this port is allowed by the firewall. I can only know the ports that the machine ...
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2answers
936 views

I ran a netstat on my server and port 80 is listening, does that mean it is open and vulnerable to attacks? [closed]

Sorry I am just getting into Web Development and trying to learn more about servers and PHP, so I downloaded the LAMP stack on an Ubuntu14 OS and started an apache2 server. tcp6 0 0 :::80 ...
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2answers
60 views

Only allow access to specific service running on computer in Demilitarized Zone over internet

If a computer (running different services such as ftp and ssh) is placed on a Demilitarized Zone, will all of its services automatically be accessed by anyone on the internet? If the answer is yes, ...
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1answer
98 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 ...
0
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1answer
98 views

How to turn of telnet and FTP on Thomson 789vn router? [closed]

I have run a port scan against a Thomson 789vn router and have noticed to my surprise that its HTTP as well as telnet and FTP ports are open. How can one turn off telnet (also FTP) using the router's ...
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2answers
207 views

Nmap stealth scan shows that port is filtered

The title is really bad, but I was able to find better. I have installed Debian on VMware, and set iptables to block any traffic except port 80 (inbound and outbound). When I run a nmap scan it shows ...
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1answer
118 views

NMAP not reporting open ports with -sS scan

Is there any reason why an -sS scan (or most others) would not report an open port that doesn't have a service attached to it? For example, in a regular -sS scan, the following port will be missing, ...
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2answers
5k views

VPN blocked ports problem

I use VPN quite often in public places where I don't want anyone to read my web traffic. However, some public places have firewalls that block ports required to establish a VPN connection (I usually ...
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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 ...
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2answers
230 views

Creating port-specific SSH authentication for the same user

I have a Linux server running SSHD and would like to know if its possible to configure it, such that from within the LAN you only need a RSA key to authenticate (on port X), but from outside the LAN ...
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1answer
728 views

MAC-address restricted port forwarding

I have an ASUS RT-AC68U router and would like to set up port forwarding, but I would like to restrict which MAC addresses can connect through that port. My use case is that I'll have a live camera, ...
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1answer
164 views

Finding the firewall port that filters internet traffic [closed]

In my office, we have static IP's for each system. All the internet traffic from our systems are filtered with a Fortiguard firewall. Is it the default gateway where the firewall is installed? How can ...
0
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1answer
245 views

Outbound Port 443 Open but Not Allowing SSH [closed]

My college wireless network has a firewall blocking all outbound ports except 443 and 80. The wired network, however, has none of these restrictions. I can connect to HTTPS sites (obviously). On my ...
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3answers
120 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?