Explanation
In stateless inspection, the firewall inspects a packet to determine the 5-tuple--source and destination IP
addresses and ports, and protocol--information contained in the packet. This static information is then
compared against configurable rules to determine whether to allow or drop the packet.
In stateless inspection the firewall examines each packet individually, it is unaware of the packets that have
passed through before it, and has no way of knowing if any given packet is part of an existing connection, is
trying to establish a new connection, or is a rogue packet.
Source:
http://www.cisco.com/c/en/us/td/docs/wireless/asr_5000/19-0/XMART/PSF/19-PSF-Admin/19-PSF-
Admin_chapter_01.html