# SYN, used to establish a TCP session. When the target responds back, we know the host is active. When it doesn't respond to ping, we know the host is blocked.
# FIN, which uses a bare packet as the probe to determine if a port is open or closed. From this we could guess what well-known services may be running based on what the open ports are generally used for. Even if the port is closed, it's required to respond with a reset packet (RST). If a RST bounces back, the port is closed. If nothing is returned, it means the port is open.
# Fragmentation scanning. When a packet reaches a host, the target has to reassemble the packet in order to make sense of it. Fragmented packets confuse these machines and can potentially bypass access controls.
Tuesday, January 25, 2022
Of TCP IP
