SYN-flood detection with Wireshark and tcpdump
Objective
Capture a TCP SYN flood against a lab web server and prove it apart from legitimate traffic bursts.
Environment
Kali attacker, Ubuntu Server target and a monitoring VM on an isolated host-only segment.
What I did
Baselined normal traffic, generated the flood, then filtered on half-open connections and compared SYN to SYN-ACK ratios per source.
Results
Isolated the spoofed sources, measured the retransmission pattern and wrote a reusable display filter for triage.
What I learned
Volume alone is not the signal — the handshake asymmetry is. That distinction is what stops a SOC from escalating a marketing campaign as an attack.
Tools
$ tcpdump -i eth0 'tcp[tcpflags] & tcp-syn != 0' 14:02:11.884 IP 10.0.0.9.443 > target.80: Flags [S] 14:02:11.884 IP 10.0.0.9.443 > target.80: Flags [S] ... 18,412 SYN / 96 SYN-ACK in 10s filter: tcp.flags.syn==1 && tcp.flags.ack==0

