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Questions tagged [firewall]

A Firewall is an application or hardware device used to inspect and filter network traffic.

4221 questions
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Debugging iptables and common firewall pitfalls?

This is a proposed Canonical Question about understanding and debugging the software firewall on Linux systems. In response to EEAA's answer and @Shog's comment that we need a suitable canonical Q&A for closing common relatively simple…
HBruijn
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Enable Ping in Windows Server Firewall?

I've just installed Windows Server 2008 on a server and I'm able to connect through Remote Desktop but can't ping. Do I need to open an special port on the firewall to be able to ping a server?
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What does "incoming" and "outgoing" traffic mean?

I've seen many resources explaining how to set up a server's firewall to allow incoming and outgoing traffic on HTTP standard ports (80 and 443), but I can't figure out why I would need either of them. Do I need to unblock both for a "regular" web…
mgibsonbr
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Relationship between bastion host and jump host

What's are the differences/similarities between a "bastion host" and a "jump host"? Are they usually used interchangeably?
kolistivra
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CentOS 7 Firewall Configuration

In CentOS 6 I could type setup from the command line and I would be presented with a set of tools, one of them being Firewall configuration. I can still do this in CentOS 7, except the list no longer includes Firewall configuration as an…
ste
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How to install gpg keys from behind a firewall?

I understand that keyservers are using the port 11371 but in many cases you are not allowed to connect to this port and you cannot add There a many cases when you cannot modify the firewall configuration. Example command that fails gpg…
sorin
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How to log the ip addresses trying to connect to a port?

Is it possible to log all IP addresses that trying to connect or connected to port "5901" in Linux Debian? How can i do that?
Gihan Lasita
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Check ufw default policy action

I know it's very easy to set the default behavior of ufw, e.g. ufw default deny, but how do I check what the default POLICY action is? It does not show in ufw status.
Sarke
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How to prevent zero day attacks

Traditionally, all anti-virus programs and IPS systems work using signature-based techniques. However, this doesn't help much to prevent zero-day attacks. Therefore, what can be done to prevent zero-day attacks?
ashmish2
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Why is our firewall (Ubuntu 8.04) rejecting the final packet (FIN, ACK, PSH) with a RST

Background, for a long time we have had problems with our firewall that sometimes keep HTTP requests hanging partially loaded until TCP times out. After tracing the traffic on the firewall I noticed that it occurs only during certain timing…
ernelli
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How to turn iptables stateless?

I'm running a Linux server that - from time to time - faces heavy load and the conntrack table overflows. Since it's iptables firewall ruleset is very simple I'd like to turn it to stateless mode. I know that iptables can operate in stateful…
tex
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What Does a Layer 3,4 Firewall do that a Layer 7 Does Not?

I'm thinking about going with a security vendor for hosted sites on my VPS, and I'm having a hard time understanding something. (Yes I know this is OSI terminology, and the sites in question are basic dental and medical practice websites with no…
David A. Wank
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Reduce firewall rules by half - one iptables rule for tcp and udp

I have a number of iptables rules on my firewall that look like this: iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT Is there a shortcut for having two rules - one for tcp and…
Big McLargeHuge
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How to setup simple firewall on Ubuntu?

Could somebody give some simple steps with configuration example how to setup simple firewall on Ubuntu (using console only)? Only ssh, http and https access should be allowed.
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How to ssh to a server which I can not directly reach?

Context I am running Ubuntu Desktop as my primary machine, which I will call D. I want to connect to server S via ssh, but the firewall is blocking me. I have access to server S, via a very cumbersome path, involving a Windows virtual machine and…
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