A common mistake when analyzing network speed/bandwidth between different applications and servers is to fully rely on the mere size of the files being transferred. In fact, one big file will transfer much faster than thousands of small files that have the same accumulated size. This depends on the overhead of reading/writing these files, building TCP/IP sessions, scanning them for viruses, etc. Furthermore, it is application dependent.
I built a small lab with an FTP server, switch, firewall, and an FTP client in which I played a bit with different file sizes. In this blog post I am showing the measured transfer times and some Wireshark graphs.
Continue reading Network Transfer: 1 Big vs. 100 Small Files
Pre-shared keys (PSK) are the most common authentication method for site-to-site IPsec VPN tunnels. So what’s to say about the security of PSKs? What is its role for the network security? How complex should PSKs be? Should they be stored additionally? What happens if an attacker catches my PSKs?
I am listing my best practice steps for generating PSKs.
Continue reading Considerations about IPsec Pre-Shared Keys
In a basic environment with a Cisco ASA firewall I am logging everything to a syslog-ng server. As there aren’t any reporting tools installed, I am using grep to filter the huge amount of syslog messages in order to get the information I want to know. In this blog post I list a few greps for getting the interesting data.
Continue reading Grep Commands for Cisco ASA Syslog Messages