Marc's Linux howtos

Simple command I don't want to forget that find a string and replace it with another using sed.

I will show you howto install PSAD to block DDOS attacks (distributed denial of service) and port scan on a webserver. Here I will use Ubuntu 8.04 LTS server but it should be very similar on other distro.

PSAD scan iptables log file to generate the attack block. The problem is that when you log ALL packets as shown in other PSAD tutorials, it will slow down considerably your server if it's busy and generate huge huge log files (growing at a rate of 1meg per second or more). With simple iptables rules, we will only log traffic that look suspicious (5 new connections in 5 seconds for example).

I created a small API for an e-store I manage (Portafixe.com) that calculate the distance between the shipping/billing location and the IP location for fraud prevention. Now i'm making it available to the public for free.

Simple bash script to monitor one or multiple webserver on different ports. I'm sure there is over 100 available programs doing this but I wanted something with small memory usage. Also, I only wanted to be notified once, notifications are receive by SMS on my cell. With the software I was using before, I was getting notified every minute until I could reach a computer and fix the problem or stop monitoring which was quite annoying.

I will show you howto install PSAD on Ubuntu 8.04 LTS server to block DDOS attacks (distributed denial of service) and port scan.

PSAD scan iptables log file to generate the attack block. The problem is that when you log ALL packets as shown in other PSAD tutorials, it will slow down considerably your server if it's busy and generate huge huge log files (growing at a rate of 1meg per second or more). With simple iptables rules, we will only log traffic that look suspicious (5 new connection in 5 second for example).