Sometimes, the standard kernel bundled with Ubuntu may not fit your environment. For example, your server is attacked regularly via bad behavior in the network. This behavior is called denial-of-service or DoS. There are so many techniques to DoS someone. The most classic one is TCP SYN flood. The effect of this attack is to full the backlog buffer in kernel. Anyway, this attack is not popular anymore. Recent kernel could handle this attack easily because it is very easy to detect TCP SYN flood. However, the worst thing I don't want to see is the attacker flood the server by established TCP connection. It is hardly to distinguish this attack from normal behavior. There are several workaround to protect the server against this attack.

1. Decrease socket timeout
2. Limit the number of concurrent connection per IP address

Ones said that cracking WEP is easy, especially when you are on Linux. I tried myself with unsuccessful because I couldn't remember the steps. Anyway, it is very easy to follow a screencast (or from ) I found last week. The screencast in YouTube is not as good as it should because of higher degree of compression so I recommend you to see the another one in WMV.

For those who want to access virtual private network based on PPTP protocol through Ubuntu Edgy Eft, you might find the most helpful network setting tool in NetworkManager.

A WinXP machine beside me has been infected by a sort of malware. I don't know what it is but I'm sure it is very annoying. Avast! didn't help me to fix this problem. It is not the fault of Avast! because it is totally free of charge and I know it is just an antivirus software. Malware may not be categorized as a virus. Anyway, I can't live with this one anymore because of its annoyance.

The most widely used virtual private network protocol is PPTP for sure. I don't know why but my friend would like to have this own VPN server for use in some special case. He has a server with Ubuntu Edgy. That's my story. Fortunately, we have Poptop aka Open Source PPTP server for Linux and it is available on Ubuntu Edgy by default.

In some situations, you might want unicast support in Access Grid because multicast is not available or impossible to implement, e.g., VPN. Fortunately, Access Grid comes with built-in unicast-to-multicast bridge support especially Access Grid 3. However, it is a kind of undocumented feature. I found a few tutorial how to run it. Actually, there are many possibility to run a bridge in Access Grid 3.