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Cisco ASDM User Guide
OL-16647-01
Chapter 2 Introduction to the Security Appliance
Firewall Functional Overview
Sending Traffic to the Advanced Inspection and Prevention Security Services Module
If your model supports the AIP SSM for intrusion prevention, then you can send traffic to the AIP SSM
for inspection. The AIP SSM is an intrusion prevention services module that monitors and performs
real-time analysis of network traffic by looking for anomalies and misuse based on an extensive,
embedded signature library. When the system detects unauthorized activity, it can terminate the specific
connection, permanently block the attacking host, log the incident, and send an alert to the device
manager. Other legitimate connections continue to operate independently without interruption. For more
information, see Configuring the Cisco Intrusion Prevention System Sensor Using the Command Line
Interface.
Sending Traffic to the Content Security and Control Security Services Module
If your model supports it, the CSC SSM provides protection against viruses, spyware, spam, and other
unwanted traffic. It accomplishes this by scanning the FTP, HTTP, POP3, and SMTP traffic that you
configure the adaptive security appliance to send to it.
Applying QoS Policies
Some network traffic, such as voice and streaming video, cannot tolerate long latency times. QoS is a
network feature that lets you give priority to these types of traffic. QoS refers to the capability of a
network to provide better service to selected network traffic.
Applying Connection Limits and TCP Normalization
You can limit TCP and UDP connections and embryonic connections. Limiting the number of
connections and embryonic connections protects you from a DoS attack. The security appliance uses the
embryonic limit to trigger TCP Intercept, which protects inside systems from a DoS attack perpetrated
by flooding an interface with TCP SYN packets. An embryonic connection is a connection request that
has not finished the necessary handshake between source and destination.
TCP normalization is a feature consisting of advanced TCP connection settings designed to drop packets
that do not appear normal.
Enabling Threat Detection
You can configure scanning threat detection and basic threat detection, and also how to use statistics to
analyze threats.
Basic threat detection detects activity that might be related to an attack, such as a DoS attack, and
automatically sends a system log message.
A typical scanning attack consists of a host that tests the accessibility of every IP address in a subnet (by
scanning through many hosts in the subnet or sweeping through many ports in a host or subnet). The
scanning threat detection feature determines when a host is performing a scan. Unlike IPS scan detection
that is based on traffic signatures, the security appliance scanning threat detection feature maintains an
extensive database that contains host statistics that can be analyzed for scanning activity.
The host database tracks suspicious activity such as connections with no return activity, access of closed
service ports, vulnerable TCP behaviors such as non-random IPID, and many more behaviors.
You can configure the security appliance to send system log messages about an attacker or you can
automatically shun the host.