Cisco ASA 5505 Configuration Manual page 171

Chapter 5 Configuring the Transparent or Routed Firewall
The packet is denied because there is no access list permitting the outside host, and the adaptive
3.
security appliance drops the packet.
4. If the outside user is attempting to attack the inside network, the adaptive security appliance
employs many technologies to determine if a packet is valid for an already established session.
OL-20339-01
Cisco ASA 5500 Series Configuration Guide using ASDM
Firewall Mode Examples
5-25