![]() *Note: IP’s have been randomized to ensure privacy. Goto Statistics -> Summary on the menu bar to understand the rate you are looking at. Analysis of an ACK flood in Wireshark – Filters Generally what is seen is a high rate of SYN packets and a slightly lesser rate of SYN-ACK packets coming from the targeted server. The acknowledgment number field is nonzero while the ACK flag is not set. The echoed key in the ACK of the MPTCP handshake does not match the key of the SYN/ACK. “Image 3 – SYN Flood stats”Ī typical SYN flood running against an unsuspecting host will look similar to the above analysis. Display Filter Reference: Transmission Control Protocol. It includes the returning SYN-ACK packets as well. The capture analyzed is 14 seconds long and the average number of packets per second are at 355, with a rate of around 161Kbps. “Image 2 – SYN-ACK packet received”Īs seen in Image 3. Transmission Control Protocol (TCP) Synchronized (SYN) Flood has become a problem to the network management to defend the network server from being attacked. The reason this SYN-ACK packet is received in response to the original SYN packet is because the victim considers this packet to be a legitimate connection request, and thus responds with a SYN-ACK in accordance with the TCP Handshake. In Image 2 you can see the victim responding with an SYN-ACK packet. “Image 1 – example of single SYN packet being sent to port 80” Notice the rate at which the packets are sent. The sequence number of the TCP SYN segment is 0 since it is used to imitate the TCP connection between the client computer and gaia.cs. In Image 1 below, you can see the flood of SYN packets coming from a single source. The following images depict a high rate of SYN packets being sent from a single source IP towards a single destination IP. Technical Analysisīelow an analysis of an SYN flood is shown. Client initiated a connection to server, server immediately acked (SYN+ACK), but client reset this packet. This leaves the TCP backlog saturated and the server and/or daemon attacked will not be able to receive any new connections. This is done by sending numerous TCP-SYN requests toward targeted services while spoofing the attack packets source IP. SYN flood is a DDoS attack aimed at consuming connection resources on the backend servers themselves and on stateful elements, like FW and Load balancers. ![]()
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