Server Fault Stack Exchange
Server Fault Stack Exchange

Questions tagged [firewall]

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

4123 questions
277
votes
15 answers

How to Unban an IP properly with Fail2Ban

I'm using Fail2Ban on a server and I'm wondering how to unban an IP properly. I know I can work with IPTables directly: iptables -D fail2ban-ssh But is there not a way to do it with the fail2ban-client? In the manuals it states something…
psp
  • 3,033
  • 3
  • 14
  • 14
196
votes
22 answers

Is it normal to get hundreds of break-in attempts per day?

I just checked my server's /var/log/auth.log and found that I'm getting over 500 failed password/break-in attempt notifications per day! My site is small, and its URL is obscure. Is this normal? Should I be taking any measures?
Kyle Cureau
  • 1,537
  • 3
  • 11
  • 15
139
votes
11 answers

best way to clear all iptables rules

I currently have this snippet: # flush all chains iptables -F iptables -t nat -F iptables -t mangle -F # delete all chains iptables -X Is there a possibility that some impervious rule will stay alive after running this? The idea is to have a…
kagali-san
  • 1,921
  • 5
  • 17
  • 20
121
votes
4 answers

How to check if a port is blocked on a Windows machine?

On the Windows platform, what native options to I have to check if a port (3306, for example) on my local machine (as in localhost), is being blocked?
Boris Pavlović
  • 1,323
  • 2
  • 9
  • 8
114
votes
7 answers

REJECT vs DROP when using iptables

Is there any reason why I would want to have iptables -A INPUT -j REJECT instead of iptables -A INPUT -j DROP
Mike B
  • 11,570
  • 42
  • 106
  • 165
109
votes
4 answers

What firewall ports need to be open to allow access to external git repositories?

What firewall port(s) need to be open to allow access to external git repositories?
markdorison
  • 1,225
  • 2
  • 8
  • 7
108
votes
20 answers

Why should I firewall servers?

PLEASE NOTE: I'm not interested in making this into a flame war! I understand that many people have strongly-held beliefs about this subject, in no small part because they've put a lot of effort into their firewalling solutions, and also because…
Ernie
  • 5,324
  • 6
  • 30
  • 37
102
votes
8 answers

Which ports do I need to open in the firewall to use NFS?

I'm running Ubuntu 11.10 - setting up NFS to share a directory among many other servers. Which ports are required to be opened on the firewall?
kenny
  • 1,133
  • 2
  • 8
  • 6
93
votes
7 answers

SSH from A through B to C, using private key on B

I'm looking for a simple way to SSH from my local machine, A, through a proxy, B, to a destination host, C. The private key that goes with the public key on C is on B, and I can't put that key on my local machine. Any tips? Also, I'd like to be…
wrangler
  • 2,920
  • 5
  • 23
  • 20
80
votes
2 answers

How to open port for a specific IP address with firewall-cmd on CentOS?

I would like to open port 4567 for the IP address 1.2.3.4 with the firewall-cmd command on a CentOS 7.1 server. How can I achieve this, as the documentation I could find was too specific on this?
Michaël Perrin
  • 903
  • 1
  • 7
  • 7
69
votes
4 answers

How to PREPEND rules rather than APPEND using iptables?

Pretty basic question: how to PREPEND rules on IPTABLES rather than to APPEND? I have DROP statements at the bottom of my rules. I have a software to add new rules but adding rules after DROP statements isn't good. Every time I want to add a new…
ale
  • 883
  • 2
  • 10
  • 13
69
votes
1 answer

What is the difference between a Source NAT, Destination NAT and Masquerading?

What is the difference between a Source NAT, Destination NAT and Masquerading? For example, I thought IP Masqurading was what they used to call it in Linux? But what confuses me is that in our Astaro firewall there is IP Masquarading as well as NAT…
hookenz
  • 14,132
  • 22
  • 86
  • 142
67
votes
4 answers

Windows equivalent of iptables?

Dumb question: Is there an equivalent of iptables on Windows? Could I install one via cygwin? The real question: how can I accomplish on Windows what I can accomplish via iptables? Just looking for basic firewall functionality (e.g. blocking certain…
Aaron F.
  • 895
  • 2
  • 8
  • 9
66
votes
8 answers

What steps do you take to secure a Debian server?

I am installing a Debian server which is connected directly to the Internet. Obviously I want to make it as secure as possible. I would like you guys/gals to add your ideas to secure it and what programs you use for it. I want part of this question…
Thomaschaaf
  • 3,012
  • 5
  • 29
  • 24
65
votes
2 answers

iptables: difference between NEW, ESTABLISHED and RELATED packets

Part of a firewall on a server : iptables -A INPUT -p tcp --dport 22 -m state NEW --state -m recent --set iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 100 --hitcount 10 -j DROP When I search online I always…
Kris
  • 1,347
  • 3
  • 15
  • 16
1
2 3
…
99 100