Setting the Default Intrusion Policy for Access Control
License:
Any
Each access control policy uses its
default intrusion policy
to initially inspect traffic before the system can determine exactly how to inspect that traffic. This is needed because sometimes the system must process the first few packets in a connection,
allowing them to pass
, before it can decide which access control rule (if any) will handle the traffic. However, so that these packets do not reach their destination uninspected, you can use an intrusion policy—called the default intrusion policy—to inspect them and generate intrusion events.
A default intrusion policy is especially useful when performing application control and URL filtering, because the system cannot identify applications or filter URLs before a connection is fully established between the client and the server. For example, if a packet matches all the other conditions in an access control rule with an application or URL condition, it and subsequent packets are allowed to pass until the connection is established and application or URL identification is complete, usually 3 to 5 packets.
The system inspects these allowed packets with the default intrusion policy, which can generate events and, if placed inline, block malicious traffic. After the system identifies the access control rule or default action that should handle the connection, the remaining packets in the connection are handled and inspected accordingly.
When you create an access control policy, its default intrusion policy depends on the default action you
first
chose. Initial default intrusion policies for access control are as follows:
-
Balanced Security and Connectivity (a system-provided policy) is the default intrusion policy for an access control policy where you first chose the
Intrusion Prevention
default action.
-
No Rules Active is the default intrusion policy for an access control policy where you first chose the
Block all traffic
default action. Although choosing this option disables intrusion inspection on the allowed packets described above, it can improve performance if you are not interested in intrusion data.
Note If you are not performing intrusion inspection, keep the No Rules Active policy as your default intrusion policy. For more information, see Troubleshooting Access Control Policies and Rules.
Note that if you change your default action after you create the access control policy, the default intrusion policy does
not
automatically change. To change it manually, use the access control policy’s advanced options.
To change an access control policy’s default intrusion policy:
Step 1 In the access control policy where you want to change the default intrusion policy, select the
Advanced
tab, then click the edit icon (
) next to the Network Analysis and Intrusion Policies section.
The Network and Analysis Policies dialog box appears.
Step 2 From the
Intrusion Policy used before Access Control rule is determined
drop-down list, select a default intrusion policy. You can choose a system- or user-created policy.
Note that if you choose a user-created policy, you can click an edit icon (
) to edit the policy in a new window. You cannot edit system-provided policies.
Caution Do
not use
Experimental Policy 1
unless instructed to do so by a Cisco representative. Cisco uses this policy for testing.
Step 3 Click
OK
to save your changes.
You must apply the access control policy for your changes to take effect.
Customizing Preprocessing with Network Analysis Policies
License:
Any
Network analysis policies
govern how traffic is decoded and preprocessed so that it can be further evaluated, especially for anomalous traffic that might signal an intrusion attempt. This traffic preprocessing occurs after Security Intelligence blacklisting and traffic decryption, but before intrusion policies inspect packets in detail. By default, the system-provided Balanced Security and Connectivity network analysis policy applies to
all
traffic handled by an access control policy.
Tip The system-provided Balanced Security and Connectivity network analysis policy and the Balanced Security and Connectivity intrusion policy work together and can both be updated in intrusion rule updates. However, the network analysis policy governs mostly preprocessing options, whereas the intrusion policy governs mostly intrusion rules.
A simple way to tune preprocessing is to create and use a custom network analysis policy as the default; see Creating a Custom Network Analysis Policy. Tuning options available vary by preprocessor.
For advanced users with complex deployments, you can create multiple network analysis policies, each tailored to preprocess traffic differently. Then, you can configure the system to use those policies to govern the preprocessing of traffic using different security zones or networks.
To accomplish this, you add custom
network analysis rules
to your access control policy. Each rule has:
-
a set of rule conditions that identifies the specific traffic you want to preprocess
-
an associated network analysis policy that you want to use to preprocess traffic that meets all the rules’ conditions
When it is time for the system to preprocess traffic, it matches packets to network analysis rules in top-down order by rule number. Traffic that does not match any network analysis rules is preprocessed by the default network analysis policy.
Note If you disable a preprocessor but the system needs to evaluate preprocessed packets against an enabled intrusion or preprocessor rule, the system automatically enables and uses the preprocessor although it remains disabled in the network analysis policy interface. Tailoring preprocessing, especially using multiple custom network analysis policies, is an advanced task. Because preprocessing and intrusion inspection are so closely related, you must be careful that you allow the network analysis and intrusion policies examining a single packet to complement each other. For more information, see Limitations of Custom Policies.
For more information, see the following sections:
Setting the Default Network Analysis Policy for Access Control
License:
Any
By default, the system-provided Balanced Security and Connectivity network analysis policy applies to all traffic handled by an access control policy. If you add network analysis rules to tailor traffic preprocessing options, the default network analysis policy preprocesses all traffic not handled by those rules.
An access control policy’s advanced settings allow you to change this default policy.
To change an access control policy’s default network analysis policy:
Step 1 In the access control policy where you want to change the default network analysis policy, select the
Advanced
tab, then click the edit icon (
) next to the Network Analysis and Intrusion Policies section.
The Network and Analysis Policies dialog box appears.
Step 2 From the
Default Network Analysis Policy
drop-down list, select a default network analysis policy. You can choose a system- or user-created policy.
Note that if you choose a user-created policy, you can click an edit icon (
) to edit the policy in a new window. You cannot edit system-provided policies.
Caution Do
not use
Experimental Policy 1
unless instructed to do so by a Cisco representative. Cisco uses this policy for testing.
Step 3 Click
OK
to save your changes,.
You must apply the access control policy for your changes to take effect.
Specifying Traffic to Preprocess Using Network Analysis Rules
License:
Any
Within your access control policy’s advanced settings, you can use network analysis rules to tailor preprocessing configurations to network traffic. Similar to access control rules, network analysis rules are numbered, starting at 1.
When it is time for the system to preprocess traffic, it matches packets to network analysis rules in top-down order by ascending rule number, and preprocesses traffic according to the first rule where all the rule’s conditions match. The conditions you can add to a rule are described in the following table.
Table 20-1 Network Analysis Rule Condition Types
|
|
|
Zones
|
entering or leaving a device via an interface in a specific security zone
|
A security zone is a logical grouping of one or more interfaces according to your deployment and security policies. To build a zone condition, see Preprocessing Traffic Per Zone.
|
Networks
|
by its source or destination IP address
|
You can explicitly specify IP addresses. To build a network condition, see Preprocessing Traffic Per Network.
|
If you do not configure a particular condition for a rule, the system does not match traffic based on that criterion. For example, a rule with a network condition but no zone condition evaluates traffic based on its source or destination IP address, regardless of its ingress or egress interface. Traffic that does not match any network analysis rules is preprocessed by the default network analysis policy.
To add a custom network analysis rule:
Step 1 In the access control policy where you want to create custom preprocessing configurations, select the
Advanced
tab, then click the edit icon (
) next to the Intrusion and Network Analysis Policies section.
The Network and Analysis Policies dialog box appears. If you have not added any custom network analysis rules, the module interface indicates that you have
No Custom Rules
, otherwise it displays how many you have configured.
Tip Click Network Analysis Policy List to display the Network Analysis Policy page in a new window. Use this page to view and edit your custom network analysis policies; see Managing Network Analysis Policies
Step 2 Next to
Network Analysis Rules
, click the statement that indicates how many custom rules you have.
The dialog box expands to show the custom rules, if any.
Step 3 Click
Add Rule
.
The network analysis rule editor appears.
Step 4 Build your rule’s conditions. You can restrict NAP preprocessing using the following criteria:
Step 5 Associate a network analysis policy with the rule by clicking the
Network Analysis
tab and choosing a policy from the
Network Analysis Policy
drop-down list.
The system uses the network analysis policy you choose to preprocess traffic that meets all the rule’s conditions. Note that if you choose a user-created policy, you can click an edit icon (
) to edit the policy in a new window. You cannot edit system-provided policies.
Caution Do
not use
Experimental Policy 1
unless instructed to do so by a Cisco representative. Cisco uses this policy for testing.
Step 6 Click
Add
.
The rule is added after any other rules. To change the rule’s evaluation order, see Managing Network Analysis Rules.
Preprocessing Traffic Per Zone
License:
Any
Zone conditions in network analysis rules allow you to preprocess traffic by its source and destination security zones. A security zone is a grouping of one or more interfaces. For more information on creating zones, see Working with Security Zones.
You can add a maximum of 50 zones to each of the
Source Zones
and
Destination Zones
in a single zone condition:
-
To match traffic
leaving
the device from an interface in the zone, add that zone to
Destination Zones
. Note that because devices deployed passively do not transmit traffic, you cannot use a zone comprised of passive interfaces in a
Destination Zone
condition.
-
To match traffic
entering
the device from an interface in the zone, add that zone to
Source Zones
.
If you add both source and destination zone conditions to a rule, matching traffic must originate from one of the specified source zones and egress through one of the destination zones.
Warning icons (
) indicate invalid configurations, such as zones that contain no interfaces. For details, see Troubleshooting Access Control Policies and Rules.
To preprocess traffic by zone:
Step 1 In the access control policy where you want to preprocess traffic by zone, create a new network analysis rule or edit an existing rule.
For detailed instructions, see Specifying Traffic to Preprocess Using Network Analysis Rules.
Step 2 In the network analysis rule editor, select the
Zones
tab.
The Zones tab appears.
Step 3 Find and select the zones you want to add from the
Available Zones
.
To search for zones to add, click the
Search by name
prompt above the
Available Zones
list, then type a zone name. The list updates as you type to display matching zones.
Click to select a zone. To select multiple zones, use the
Shift
and
Ctrl
keys, or right-click and then select
Select All
.
Step 4 Click
Add to Source
or
Add to Destination
to add the selected zones to the appropriate list.
You can also drag and drop selected zones.
Step 5 Save or continue editing the rule.
You must apply the access control policy for your changes to take effect; see Deploying Configuration Changes.
Preprocessing Traffic Per Network
License:
Any
Network conditions in network analysis rules allow you to preprocess traffic by its source and destination IP address. You can manually specify the source and destination IP addresses for the traffic you want to preprocess, or you can configure network conditions with network objects, which are reusable and associate a name with one or more IP addresses and address blocks.
Tip After you create a network object, you can use it not only to build network analysis rules, but also to represent IP addresses in various other places in the system’s module interface. You can create these objects using the object manager; you can also create network objects on-the-fly while you are configuring network analysis rules. For more information, see Working with Network Objects.
You can add a maximum of 50 items to each of the
Source Networks
and
Destination Networks
in a single network condition:
-
To match traffic from an IP address, configure
Source Networks
.
-
To match traffic to an IP address, configure
Destination Networks
.
If you add both source and destination network conditions to a rule, matching traffic must originate from one of the specified IP addresses and be destined for one of the destination IP addresses.
When building a network condition, warning icons (
) indicate invalid configurations. For details, see Troubleshooting Access Control Policies and Rules.
To preprocess traffic by network:
Step 1 In the access control policy where you want to preprocess traffic by network, create a new network analysis rule or edit an existing rule.
For detailed instructions, see Specifying Traffic to Preprocess Using Network Analysis Rules.
Step 2 In the network analysis rule editor, select the
Networks
tab.
The Networks tab appears.
Step 3 Find and select the networks you want to add from the
Available Networks
, as follows:
-
To add a network object on the fly, which you can then add to the condition, click the add icon (
) above the
Available Networks
list; see Working with Network Objects.
-
To search for networks to add, click the
Search by name or value
prompt above the
Available Networks
list, then type an object name or the value of one of the object’s components. The list updates as you type to display matching objects.
To select an object, click it. To select multiple objects, use the Shift and Ctrl keys, or right-click and then select
Select All
.
Step 4 Click
Add to Source
or
Add to Destination
to add the selected objects to the appropriate list.
You can also drag and drop selected objects.
Step 5 Add any source or destination IP addresses or address blocks that you want to specify manually.
Click the
Enter an IP address
prompt below the
Source Networks
or
Destination Networks
list; then type an IP address or address block and click
Add
.
Step 6 Save or continue editing the rule.
You must apply the access control policy for your changes to take effect; see Deploying Configuration Changes.
Managing Network Analysis Rules
License:
Any
A network analysis rule is simply a set of configurations and conditions that specifies how you preprocess traffic that matches those qualifications. You create and edit network analysis rules in the advanced options in an existing access control policy. Each rule belongs to only one policy.
To edit a custom network analysis rule:
Step 1 In the access control policy where you want to change your custom preprocessing configurations, select the
Advanced
tab, then click the edit icon (
) next to the Intrusion and Network Analysis Policies section.
The Network and Analysis Policies dialog box appears. If you have not added any custom network analysis rules, the module interface indicates that you have
No Custom Rules
; otherwise, it displays how many you have configured.
Step 2 Next to
Network Analysis Rules
, click the statement that indicates how many custom rules you have.
The dialog box expands to show the custom rules, if any.
Step 3 Edit your custom rules. You have the following options:
-
To edit a rule’s conditions, or change the network analysis policy invoked by the rule, click the edit icon (
) next to the rule.
-
To change a rule’s order of evaluation, click and drag the rule to the correct location. To select multiple rules, use the Shift and Ctrl keys.
-
To delete a rule, click the delete icon (
) next to the rule.
Step 4 Click
OK
to save your changes.
You must apply the access control policy for your changes to take effect; see Deploying Configuration Changes.