Haben Sie mal Netzwerkmitschnitte untersucht, ohne zu wissen, was genau Sie suchen? Mit Wireshark wird das leicht zu einer Odyssee: Das Analysewerkzeug filtert zwar fabelhaft, reagiert bei großen Datenmengen aber schnell zäh.
Was bei solchen Problemstellungen hilft ist: tshark! Ein Tool, mit welchem Sie auch große Packet Captures einfach anhand gängiger Kriterien durchforsten können.
Continue reading Netzwerkmitschnitte mit tshark analysieren
Angreifer verwenden gern Ping und Traceroute, um Server im Internet ausfindig zu machen. Das bringt viele Security-Admins in Versuchung, den Ping- und Traceroute-Verkehr mittels ihrer Firewall in ihrem Netz zu unterbinden. Doch damit behindern sie nur die Arbeit von Server-Administratoren, denn es gibt noch viel mehr Möglichkeiten, Server aufzuspüren.
Continue reading Server-Verfügbarkeit: Monitoring-Werkzeuge
Again and again, I am adding some protocol samples to the Ultimate PCAP. Just for reference. And because I can. ;D
Continue reading Again some more protocols & variants
An updated version of my Ultimate PCAP is available. It features some more network protocols that I will depict in this blog post. It’s getting more special since the most common protocols were already in there. ;)
Continue reading More Capture Details II
Some time ago I published a pcap that can be used to study basic IPv6 protocol messages such as ICMPv6 for Router Advertisements, Neighbor Solicitations, etc.: “Basic IPv6 Messages: Wireshark Capture“. You can use it to learn the basic IPv6 address assignment and layer 2 address resolution. However, that pcap does not include any upper layer protocols.
This time I captured a few application layer protocols that I used over IPv6 rather than over legacy IP. Common user protocols such as DNS, HTTP/S, IMAP, SMTP (with STARTTLS), as well as some network administration protocols: SSH, SNMP, and Ping. It is not that interesting at all ;) though you can use it to have some examples for Wireshark to prove that those application protocols are almost the same when run above IPv6 compared to IPv4.
Continue reading IPv6 Upper Layer Protocol Samples
It is not easy to sync the own files/mails/contacts/calendars/etc. in order to keep them private (not via a public cloud) and to create regular backups. Furthermore, every solution must be easy to use (at least for my wife ;)) and reliable.
Following is my approach for keeping my files in sync and private. What are yours?
Continue reading In Sync 2017
DNS-based Authentication of Named Entities (DANE) is a great feature that uses the advantages of a DNSSEC signed zone in order to tell the client which TLS certificate he has to expect when connecting to a secure destination over HTTPS or SMTPS. Via a secure channel (DNSSEC) the client can request the public key of the server. This means, that a Man-in-the-Middle attack (MITM) with a spoofed certificate would be exposed directly, i.e., is not possible anymore. Furthermore, the trust to certificate authorities (CAs) is not needed anymore.
In this blog post, I will show how to use DANE and its DNS records within an authoritative DNS server to provide enhanced security features for the public.
Continue reading How to use DANE/TLSA
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
During the last few months, the concept of Perfect Forward Secrecy (PFS) was presented in many newspapers and guidelines. This concept is related to the session key generation for SSL/TLS as well as for IPsec tunnels. And even though many of these articles describe the benefit of PFS, I was still missing a picture that shows the main difference between the classical key exchange via RSA and the exchange via Diffie-Hellman with PFS. So, here comes my poster. ;)
Continue reading At a Glance: Perfect Forward Secrecy (PFS)
I am currently in touch with a few HTTP proxy installations. As every time when troubleshooting network issues, I am looking at Wireshark on the network and trying to understand the different packets.
Here is a short overview of the differences between HTTP requests that are sent directly to the destination and HTTP requests that are sent via a proxy. Wireshark screenshots and a downloadable pcap round things up.
Continue reading At a Glance: HTTP Proxy Packets vs. Normal HTTP Packets