The other day I wanted to verify whether a service running on my Linux server was listening on IPv6 as well as IPv4. It turned out that it wasn’t that easy to answer – if at all.
As already pointed out in my NTP intro blogpost Why should I run own NTP Servers? it is crucial to leverage NTP authentication to have the highest trustworthiness of your time distribution all over your network. Hence the first step is to enable NTP authentication on your own stratum 1 NTP servers, in my case two Raspberry Pis with DCF77/GPS reference clocks.
As always when you’re running your own services you should update them regularly to have all known bugs fixed and security issues thwarted. Same for NTP servers based on Linux, as in my case running on Raspberry Pis. Especially when you’re actively joining the NTP pool project with your NTP servers you have to update them to the latest version of ntp since you might be misused for well-known DDoS attacks or other security-related bugs.
So, what’s this all about? You can simply do an “apt upgrade”, don’t you? Well, unluckily the ntp packages within the Linux distributions are not always updated to the latest versions. Hence you need to compile the ntp software by yourself to have the latest release running. Still not that hard, though it requires a bit more attention.
If you’re running your own DNS resolver you’re probably interested in some benchmark tests against it, such as: how fast does my own server (read: Raspberry Pi) answer to common DNS queries compared to 188.8.131.52.
In this blogpost I am showing how to use two tools for testing/benchmarking DNS resolvers: namebench & dnseval. I am listing the defaults, giving some hints about them and showing examples in which I tested some private and public DNS resolvers: a Fritzbox router, a Raspberry Pi with Unbound, Quad9, OpenDNS, and Google Public DNS.
To solve the chicken-or-egg problem for DNSSEC from the other side, let’s use an authoritative DNS server (BIND) for signing DNS zones. This tutorial describes how to generate the keys and configure the “Berkeley Internet Name Domain” (BIND) server in order to automatically sign zones. I am not explaining many details of DNSSEC at all, but only the configuration and verification steps for a concrete BIND server.
It is really easy to tell BIND to do the inline signing. With this option enabled, the admin can still configure the static database for his zone files without any relation to DNSSEC. Everything with signing and maintaining is fully done by BIND without any user interaction. Great.
This is a basic tutorial on how to install BIND, the Berkeley Internet Name Domain server, on a Ubuntu server in order to run it as an authoritative DNS server. It differs from other tutorials because I am using three servers (one as a hidden primary and two secondaries as the public accessible ones), as well as some security such as denying recursive lookups and public zone transfers, as well as using TSIG for authenticating internal zone transfers. That is, this post is not an absolute beginner’s guide.
This blog post is about using NetFlow for sending network traffic statistics to an nProbe collector which forwards the flows to the network analyzer ntopng. It refers to my blog post about installing ntopng on a Linux machine. I am sending the NetFlow packets from a Palo Alto Networks firewall.
My current ntopng installation uses a dedicated monitoring ethernet port (mirror port) in order to “see” everything that happens in that net. This has the major disadvantage that it only gets packets from directly connected layer 2 networks and vlans. NetFlow on the other hand can be used to send traffic statistics from different locations to a NetFlow flow collector, in this case to the tool nProbe. This single flow collector can receive flows from different subnets and routers/firewalls and even VPN tunnel interfaces, etc. However, it turned out that the “real-time” functionalities of NetFlow are limited since it only refreshes flows every few seconds/bytes, but does not give a real-time look at the network. It should be used only for statistics but not for real-time troubleshooting.
Some time ago I published a post introducing ntopng as an out-of-the-box network monitoring tool. I am running it on a Knoppix live Linux notebook with two network cards. However, I have a few customers that wanted a persistent installation of ntopng in their environment. So this is a step-by-step tutorial on how to install ntopng on a Ubuntu server with at least two NICs.
Roundcube is an email webclient which is easy and intuitive to use. I am using it for my private mails, connecting via IMAP and SMTP to my hoster. One of the great advantages is the “flag” option which is synchronized via IMAP to my Apple devices.
Following is a step-by-step installation guide for Roundcube plus an update scenario. It is a kind of “memo for myself”, but hopefully, others can use it as well.
If you want to use you own ownCloud installation, you can find several documentation on the Internet on how to set up this server, e.g. the official ownCloud documentation, or installation guides such as this or that or here. But none of these page alone provided enough information for installing a secure server completely from the beginning.
So here comes my step-by-step guide which surely won’t be complete, too. ;) However, hopefully it will help other people while searching for their way to install ownCloud. Additionally I am showing how to upgrade an ownCloud server.
Some time ago I installed a new firewall at the customer’s site. Meanwhile the customer was interested in the flows that are traversing through the firewall right now. Oh. Good question. Of course it is easy to filter through log messages of firewalls, but theses logs are only for finished sessions. Yes, there are “session browsers” or the like on all firewalls, but they are not nice and handy to analyze the sessions in real-time.
The solution was to bring a network analyzer on a mirror port near to the firewall. I decided to use ntopng running on the live Linux distribution Knoppix. Great choice! An old notebook with two network adapters fits perfectly. A handful commands and you’re done:
While parsing logfiles on a Linux machine, several commands are useful in order to get the appropriate results, e.g., searching for concrete events in firewall logs.
In this post, I list a few standard parsing commands such as grep, sort, uniq, or wc. Furthermore, I present a few examples of these small tools. However, it’s all about try and error when building large command pipes. ;)
This is a tutorial on how to configure the GlobalProtect Gateway on a Palo Alto firewall in order to connect to it from a Linux computer with vpnc.
Short version: Enable IPsec and X-Auth on the Gateway and define a Group Name and Group Password. With this two values (and the gateway address), add a new VPN profile within vpnc on the Linux machine. Login with the already existing credentials.
Long version with screenshots comes here:
This post describes how to add a Linux machine to the MRTG/Routers2 monitoring server. First, the host must be able to process SNMP requests. Then, a *.cfg file for MRTG/Routers2 is created by running the “cfgmaker” tool with a host-template. Since a few values are wrong in the cfgmaker file, I also explain how to correct them. Finally, I am adding the mrtg-ping-probe lines to the configuration.