I am using Nmap every time I installed a new server/appliance/whatever in order to check some unknown open ports from the outside. In most situations I am only doing a very basic run of Nmap without additional options or NSE scripts.
Likewise I am interested in how the Nmap connections appear on the wire. Hence I captured a complete Nmap run (TCP and UDP) and had a look at it with Wireshark. If you’re interested too, feel free to download the following pcap and have a look at it by yourself. At least I took some Wireshark screenshots to give a first glance about the scan.
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As a network administrator I know that there are SSH fingerprints. And of course I know that I must verify the fingerprints for every new connection. ;) But I did not know that there are so many different kinds of fingerprints such as md5- or sha-hashed, represented in base64 or hex, and of course for each public key pair such as RSA, DSA, ECDSA, and Ed25519. Uh, a bit too complicated at a first glance. Hence I draw a picture.
Continue reading SSH Key Fingerprints
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.
Continue reading DNSSEC Signing w/ BIND
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 slaves 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.
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I initially stored my ownCloud data on an external NTFS hard disk. (Yes, this was not a good idea at all.) After some time now I wanted to move the files to a bigger ext4 drive on the same machine. Unluckily there are many posts and articles that are really irritating on the Internet, such as: 1, 2, 3, 4, 5. At least I found some promising hints at the official GitHub forums (this and that) and gave it a try:
Continue reading ownCloud Data Directory
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.
Continue reading ntopng Installation
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.
Continue reading Roundcube Installation Guide
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.
Continue reading Yet another ownCloud Installation Guide
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:
Continue reading Out of the Box Network Analyzer “ntopng”
When explaining IPv6 I am always showing a few Wireshark screenshots to give a feeling on how IPv6 looks like. Basically the stateless autoconfiguration feature (SLAAC), DHCPv6, Neighbor Discovery, and a simple ping should be seen/understood by any network administrator before using the new protocol.
Therefore I captured the basic IPv6 autoconfiguration with a Knoppix Linux behind a Telekom Speedport router (German ISP, dual-stack) and publish this capture file here. I am using this capture to explain the basic IPv6 features.
Continue reading Basic IPv6 Messages: Wireshark Capture
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. ;)
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This post shows a guideline for a basic installation of the open source syslog-ng daemon in order to store syslog messages from various devices in a separate file for each device.
I am using such an installation for my firewalls, routers, etc., to have an archive with all of its messages. Later on, I can grep through these logfiles and search for specific events. Of course it does not provide any built-in filter or correlation features – it is obviously not a SIEM. However, as a first step it’s better than nothing. ;)
Continue reading Basic syslog-ng Installation