Notes on Understanding TCP SYN Flooding Attacks

The basis of the SYN flooding attack lies in the flaw of how the 3-way handshake initiates. The 3-way handshake is initiated at the start of a TCP connection. The third packet which completes the handshake, confirms the source's ability to receive packets at the IP address it used.

The key to success in this DoS attack is the Transmission Control Block (TCB). The TCB is a data set of structures in operations systems that holds all the information about a connection. Each TCB > 280 bytes, and can exceed 1300 bytes in other operating systems. After the first part of the 3-way hand-shake is finished, the connection is only half-open. TheIt is very important to note is that the TCB is already allocated based on reception of the SYN packet— before the connection is fully established.

 A flood of incoming SYN requests can cause the allocation of so many TCBs such that  a host's kernel memory becomes exhausted. Although there is a backlog mechanism in most operating systems, this can easily be filled up. Thus, new requests cannot be served until some TCBs can be freed up from the half open connection state.

Since TCP protocol is designed for reliability, the target host tends to wait for a long time with the half-open connections, until the 3-way handshake is completed. 

More on this article right here from Cisco.

1st Semester Performance

Finally got all my grades! So far, so good... I got all 1's!!! =)

The following are subjects which I personally feel deserve some particular attention:

Most challenging subjects - gave me a really hard time like all of my classmates:

• Network Planning
• Service Provisioning
• Data Center Computing

Most interesting ones - these are areas which really grab my attention and curiosity:

• Network Planning
• Telecom and Internet Platforms
• IP Security in Heterogeneous Networks
• Linux Networks

Subjects I need to drill deeper in:
IP Security in Heterogenous Networks
Data Center Computing

As I went through the first semester, I looked at all my strengths and my interests. I think I would like to be in IT security. In cyberspace, heroes and villains also exist. And they will always be in a struggle, trying to outdo each other. Hence, I'm going to focus my thesis around the area of Web Applications security.

Prerequisites? Programming could be one. I guess it's time that I learn another language here in Austria aside from German.