All Questions
30
questions
0
votes
0
answers
43
views
Teardrop detected from TCP ACK from myself
I'm experimenting with linux (Debian 5.10) networking to allow me to connect two networks (eg. 192.168.0.0/24 with 172.17.0.0/16) together.
Setup
In my case it is a small server with one NIC, hosting ...
- 126
0
votes
1
answer
337
views
How to send back TCP packets using iptables
I am trying to demonstrate TCP communication with a Ubuntu 18.04 box (which mocks a QNX setup) that does not have a listener installed. Consider that due to some license issues it might not be ...
2
votes
1
answer
671
views
Why does my virtual machine (Debian on Proxmox) not respond to a TCP SYN of another VM even though it arrives?
I got a very strange problem and I am out of ideas to solve it. I hope anyone over here has a helpful idea.
Some info about the virtual machines:
VM0: Debian 10 - 192.168.10.102 [+ 2 more interfaces]
...
- 41
3
votes
1
answer
1k
views
How to have Windows firewall send RST packet for blocked port
Is there any way to instruct windows firewall to send Reset packets for a blocked TCP connection instead of dropping the packet?
- 143
0
votes
1
answer
413
views
Relay TCP upload traffic and make download traffic go directly to the client
This is a supplement for iptables SNAT for UDP rule is only applied to some traffic
In fact, I have three machines:
the client
the target server
the relay server
What's my motivation for doing this?
...
- 13
0
votes
1
answer
2k
views
Block outgoing connection from server to Internet, but enable specific TCP port access from outside
I am using Mikrotik RouterOS on a Mikrotik router.
There is a server in my network from which every outgoing connection using every protocol should be disabled. I achieved this with a following rule:
/...
- 944
0
votes
1
answer
2k
views
TCP communcation - HyperV virtual machine opening port on host
Here's the summary of my fight to connect to a port on the hypervisor host from a VM hosted on the same machine:
Set up in the Hyper-V Manager:
Virtual Switch Settings
Internal
'Enable virtual LAN ...
- 11
-3
votes
1
answer
84
views
Why does my IPTables changes not deny access from all IP addresses except CloudFlare’s ranges?
I am running apache on ubuntu 18.04. I used IPtables to deny access from all IP addressed except CloudFlare’s ranges and when I run iptables -L –line-number I get
1 ACCEPT tcp – 131.0.72.0/22 anywhere ...
0
votes
1
answer
467
views
Samsung Smart TV UA43N5300ARLXL/UA43N5300ARXXL unable to connect to internet over UFW firewall
I have a home network with a Raspberry Pi at the center running Pihole and UFW. The Pihole is both the DHCP as well as DNS server.
Ever since I started using Pi Hole I've not had any issues until ...
- 21
1
vote
0
answers
2k
views
SSH fails to connect from one computer but works from other computers
Problem
I have an external VPS server running Ubuntu 18.04 with openssh-server 7.6p1. I can connect via ssh to this server from many different networks except from one particular client. This ...
- 111
0
votes
1
answer
1k
views
TCP RST when connecting via telnet to the application - Windows
I have an application running on Windows.
The application listens on port 54000.
I can connect to the application from the local machine and it works fine:
telnet 127.0.0.1 54000
Now, I am trying to ...
- 141
0
votes
2
answers
280
views
If I disable iptables its working. Which rule is making my websites a timeout?
I have a VPS with nginx but no website is working and timeout is sent. When I disable iptables everything is fine. But no idea which rule/s is taking the problem. Any help?
$sudo iptables -S
-P INPUT ...
- 1
0
votes
0
answers
216
views
Iptables configuration
Here is my iptables script. Can it be better ?
Thanks in advance !
#!/bin/bash
#iptables-restore < /etc/iptables.test.rules
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables ...
- 1
3
votes
2
answers
5k
views
Getting a UDP-only VPN to work over TCP
For a project of mine, I'm searching for possibilities to have a UDP-only VPN working over TCP (preferably on port 443 or 80). I have found the following while doing some research:
This is possible ...
- 133
0
votes
0
answers
82
views
in Debian server, IPTABLES PREROUTING behave differenty for different ports
I have following three rules in my iptables firewall
-A PREROUTING -i eth0 -p tcp -m tcp --dport 12346 -j DNAT --to-destination 11.207.2.4:12350
-A PREROUTING -i eth0 -p tcp -m tcp --dport 12348 -j ...
0
votes
0
answers
343
views
Block TCP connection to certain domain
Using ProcMon.exe, I see that I got an outgoing TCP request to
MyUser-PC.home:54988 -> ec1-51-49-47-232.eu-west-1.compute.amazonaws.com:https
And then an incoming TCP request:
MyUser-PC.home:...
- 157
1
vote
0
answers
212
views
Firewall : Is inbound required for getting response while Outbound rule already there?
I developed one MVC web application which have Web APIs and hosted in Amazon Instance and one windows application for calling those APIs for getting response from that server.
Both Web and Windows ...
1
vote
1
answer
86
views
Where do I start to troubleshoot this strange activity from my firewall?
I noticed that my firewall yesterday blocked outgoing attempts starting at port 61494 and worked its way up to 62381, making a TCP outgoing attempt at each port once. The remote IP address seems ...
- 131
0
votes
0
answers
29
views
How to know that I passed the firewall from the TCP connections?
In my company, in order to access some intranet-sites, I have first to login to webpage (which I suppose is a firewall or something) with my account. If I login from FF for example, I can access the ...
- 196
1
vote
2
answers
757
views
iptables SNAT target and TCP ACK packets
I need to establish a TCP connection where the client is spoofing its IP for all outgoing traffic. My first attempt was to add a rule to the POSTROUTING chain like so:
iptables -t nat -A POSTROUTING -...
- 11
0
votes
0
answers
981
views
How to block HTTP 302 redirection package by matching a specific string on Location?
The HTTP response I want to block has:
Header
HTTP/1.1 302 Found
Location: http://www.yxjiaodai.com/ad/?id=1023&url=http%3A//a1819.oadz.com/link/C/1819/3081547/dtMdon4l79FwsIo2JXEHqtdp5eQ_/p007/...
- 193
1
vote
1
answer
3k
views
RPC Connection Filtered with no Firewalls
I have a workstation (PC1) that cannot communicate with a domain controller over RPC (TCP/135).
C:\PortQryV2> portqry.exe -n 192.168.1.1 -p tcp -o 135
Querying target system called:
192.168.1.1
...
0
votes
0
answers
1k
views
Firewall is blocking echo request on port 7 (TCP)
I have an app which needs to receive a message back from the server. With the firewall on, I do not get the message back. If I turn off the firewall I get the request back.
I have added some rules ...
- 111
5
votes
2
answers
7k
views
Detect what outgoing ports are bypassed by firewall
My school has a firewall which limits most outgoing ports. There're only TCP/80, TCP/443, TCP/21 allowed. Is there's a way to find out all the outgoing port allowed by the firewall?
My current idea: ...
- 2,667
0
votes
1
answer
2k
views
Ports 1935 and 843 are getting blocked for no reason
I have Windows 7, and my computer has been blocking ports 1935 and 843 for no reason for a while now. If for example, I try to watch twitch, nothing will work because those two are getting blocked.
...
- 113
2
votes
1
answer
6k
views
using iptables to prevent RST related to a specific port
I have a program which uses libpcap to capture incoming TCP SYN packets, these SYN packets are destined for a specific port.
But I have no tcp listening socket for that port, so in practice, the OS ...
- 3,055
0
votes
1
answer
1k
views
TCPview: Some strange process?
I just install the TCPview to check if there are any abnormalities in my computer connections, and there are something looks strange:
There are 2-3 process that show the following status from time to ...
- 101
1
vote
1
answer
3k
views
How to listen to all ports (udp and tcp) or make them all appear open in Debian
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 ...
- 63
5
votes
1
answer
19k
views
Windows 7 firewall causing remote connection to time out; should refuse connection
The Windows 7 Firewall is running with default options to allow outbound connections and block incoming connections. I have a process trying to connect regularly from within my local network, which is ...
- 53
0
votes
3
answers
1k
views
What typically uses port 44380?
A company just asked me to open port 44380 in my firewall so that their software could work.
This made me wonder... what is the customary use for port 44380?
- 15.8k