Custom Rules

Use custom rules to tailor how Security identifies malicious traffic. This provides added flexibility for threat identification that allows you to target malicious traffic with minimal impact to legitimate traffic. Custom threat identification combined with rapid testing and deployment enables you to quickly address long-term and zero-day vulnerabilities.

Custom Rule Sets #

A custom rule set defines how threats will be identified through rules. Each rule contains:

• Up to 6 conditions that define threat identification criteria.

• A rule ID and message that will be associated with threats identified by this rule.

  Assigning a unique ID and message to each rule makes it easy to identify threats detected as a result of a specific rule.

  A rule ID must be a number between 66,000,000 and 66,999,999.

Threat Identification #

Security identifies a threat when a request satisfies at least one rule in a custom rule set. A rule is satisfied when a match is found for one or more variable(s) in each condition.

Example #1:

This example assumes that your custom rule set contains the following two rules:

Rule	Description
1	This rule contains a single condition with a single variable.
2	This rule contains the following conditions: 1. The first condition contains a single variable. 2. The second condition contains two variables.

Assuming the above configuration, Security identifies a threat under either of the following circumstances:

• A match is found for the variable defined in the first rule’s condition.

• A match is found for the variable defined in the second rule’s first condition.

  AND

  A match is found for either of the variables defined in the second rule’s second condition.

Conditions #

A condition determines how requests will be identified through variables, operators, match values, transformations, and negative matching.

Variables

A variable identifies the request element that Security will analyze. We support the following request elements:

• ASN: Identifies requests by the Autonomous System Number (ASN) associated with the client’s IP address.

  Specify a regular expression to match for multiple ASNs.

  Example:

  Use the following pattern to match for requests from 15133 and 14153: 15133|14153

• Country: Identifies requests by the country from which the request originated. Specify the desired country using a country code.

  Specify a regular expression to match for multiple country codes.

  Example:

  Use the following pattern to match for requests from the United States, Canada, and Mexico: US|CA|MX

• IP address: Identify requests by the requester’s IPv4 and/or IPv6 address.

  • Specify a comma-delimited list of the desired IP address(es) using standard IPv4/IPv6 and CIDR notation.
  • Specify a subnet by appending a slash (/) and the desired bit-length of the prefix (e.g., 11.22.33.0/22).
  • Do not specify more than 1,000 IP addresses or IP blocks.
  Identifying requests by IP address is only supported when a condition contains a single variable.

  Example: 192.0.2.20,203.0.113.0/24,2001:DB8::/32

• Request body parsed: Match against all or specific key-value pair(s) in the request body for a URL-encoded or JSON POST request:

  • All: Do not specify a key within this variable and specify the desired value or pattern within the Match value option.

  • Specific Key-Value Pair: Define the name of the desired key within this variable and specify the desired value or pattern within the Match value option.

    Setting up a request body parsed variable also allows you to define whether Security uses a regular expression, a negative match, or both when comparing the value assigned to the variable against key names. Use a negative match to find requests whose payload does not contain the specified key.

  Use the Request body raw variable to match against the URL-encoded request body for any type of request (e.g., XML).

  Security only inspects the first 8 KB of the request body. You may restrict the request body for valid requests to 8 KB (8,192 bytes) through a managed rule.

  Example:

  Match against the following request body by setting the the Match value option to blue. Require that this value be assigned to the sky key by also setting the request body parsed variable to sky.

  1{
  2    "id": "srZf45oP34p",    
  3    "sky": "blue"
  4}

• Request body raw: Match against a URL-encoded request body for any type of request (e.g., XML).

  Security only inspects the first 8 KB of the request body. You may restrict the request body for valid requests to 8 KB (8,192 bytes) through a managed rule.

• Request cookies: Match against all or specific cookies.

  • All: Do not specify the desired cookie within this variable and specify the desired cookie value or pattern within the Match value option.

  • Specific Cookies: Define the name of the desired cookie within this variable and specify the desired cookie value or pattern within the Match value option.

    Setting up a cookie variable also allows you to define whether Security uses a regular expression, a negative match, or both when comparing the value assigned to the variable against cookies. Use a negative match to find requests whose payload does not contain the specified cookie.

• Request header: Match against all or specific request headers.

  • All: Do not specify the desired request header within this variable and specify the desired header value or pattern within the Match value option.

  • Specific Request Headers: Define the name of the desired request header within this variable and specify the desired header value or pattern within the Match value option.

    Setting up a request header variable also allows you to define whether Security uses a regular expression, a negative match, or both when comparing the value assigned to the variable against request headers. Use a negative match to find requests whose payload does not contain the specified request header.

• Request method: Match against request method (e.g., GET and POST).

• Request query: Match against the request’s query string. Specify the desired value or pattern within the Match value option.

• Request URI: Match against the request’s URL path and query string. Define a URL path that starts directly after the hostname. Exclude the protocol and hostname when defining this property.

  Security does not transform edge CNAME URLs to CDN URLs prior to performing this comparison.

  Sample values:

  /marketing?id=123456

  /resources/images

• Request URL path: Match against the request’s URL path. Define a URL path that starts directly after the hostname. Exclude the protocol, hostname, and query string when defining this property.

  Our service does not transform edge CNAME URLs to CDN URLs prior to performing this comparison.

  Sample values:

  /marketing

  /resources/images

Operators

An operator determines how Security will compare a match value against the request element identified by a variable.

• Begins with: A match is found when the request element starts with the specified match value.

• Contains: A match is found when the request element contains the specified match value.

• Ends with:  A match is found when the request element ends with the specified match value.

• Exact match:  A match is found when the request element is an exact match to the specified match value.

  Avoid enabling the Negative match option with the Exact match operator. This configuration will not yield the expected set of matches.

• Regex: A match is found when the request element satisfies the regular expression defined in the match value.

• Value match: A match is found when the request element occurs the exact number of times defined in the match value.

  The Value match operator should only be used when the Count option has been enabled.

Match Value

Security uses a match value to identify threats.

• Default: By default, Security compares a match value against the request element identified by a variable (e.g., URL path or a request header’s value).
• Count: Enable the Count option on a variable to compare this value against the number of times that the request element identified by a variable (e.g., a specific cookie or request header) occurs within the request.

Example:

This example assumes the following configuration:

Variable: Request header = Authentication

Match value: 1

We will now examine how the Count option affects comparisons for this configuration.

• Disabled: If the Count option has been disabled on the variable, then Security will compare the value of the Authentication request header to 1.
• Enabled: If the Count option has been enabled on the variable, then Security will compare the number of times that the Authentication request header occurred in the request to 1.

Match Transformations

Security can transform the source value before it inspects it. Select one or more of the following transformations to allow Security to compare the match value against the result of each selected transformation:

• Lowercase: Converts all uppercase characters to lowercase characters.
• None: The source value will not be modified.
• Remove nulls: Removes all null values from the source value.
• URL decode: Applies URL decoding to the source value. This transformation is useful when the source value has been URL encoded twice.

Custom Rule Administration #

You may create, modify, and delete custom rule sets.

Key information:

• Administer custom rule sets from the Custom Rules page.
• Apply a custom rule set to production traffic by adding it to a Security Application configuration and then determining how it will be enforced. Multiple Security Application configurations may use the same custom rule set. Leverage this capability to tailor security screening by application or traffic profile.
• It may take up to 2 minutes for an updated custom rule set to be applied across our entire network.

To create a custom rule set

1. Navigate to the Custom Rules page.
   1. From the Edgio Developer console, select the desired team space.
   2. From the Security section, click Custom Rules.
2. Click Add Custom Rule.
3. In the Name option, type the unique name by which this custom rule set will be identified. This name should be sufficiently descriptive to identify it when setting up a Security Application configuration.
4. Create a custom rule by clicking + Add Rule. Find the rule’s Name option and set it to a name that identifies the purpose of this rule.
5. In the Rule ID option, specify a number between 66,000,000 and 66,999,999.
6. In the Rule message option, type a brief description for this rule.
7. The default rule contains a default condition. Modify this condition to determine how Security will identify threats.

   1. From the condition’s Variable option, select the request element through which Security will identify threats.

      Learn more about variables.

   2. Certain variables (e.g., request cookies and request header) match on name and value. If you have selected this type of variable, then perform the following steps:

      1. Click + Add Match.

      2. From the Name option, type the desired name.

         For example, match for requests that contain an Authorization header by setting this option to Authorization.

      3. Optional. Mark the Negative Match option to match for requests that do not contain a matching value for the name defined in the previous step.

      4. If you specified a regular expression in the Name option, then you should mark the Regex Match option.

      5. Optional. Add another match through which this variable can be satisfied by repeating steps 7.2.1 - 7.2.4.

   3. Optional. Mark the Count option to match by the number of instances that a match is found instead of by inspecting that request element.

      Learn more.

   4. Optional. Click + Add Variable to add another variable through which this request may be satisfied. Repeat steps 7.1 - 7.3.

      If you would like to a use a different match value for this variable, then you should create a new rule. Alternatively, if you would like to require both variables prior to threat identification, then you should add it as a new condition to this rule.

   5. From the Operator option, select an operator that determines how Security will compare the match value to the request element identified by the above variable.

      Learn more.

   6. In the Match value option, type the value that will be compared against the request element identified by the above variable.

   7. From the Match transformations option, select each transformation that will be applied to the source value.

      Learn more.

   8. Optional. Mark the Negative Match option to match for requests that do not contain a matching value for the value defined in step 7.6.

8. Optional. Click + Add Condition to add another condition that must be met prior to threat identification. Repeat step 7 for this new condition.
9. Optional. Click + Add Rule to add another rule through which Security may identify threats. Repeat steps 7 and 8.
10. Click Submit.

To modify a custom rule set

1. Navigate to the Custom Rules page.

   1. From the Edgio Developer console, select the desired team space.
   2. From the Security section, click Custom Rules.

2. Click on the desired custom rule set.

3. Make the desired changes.

   Key tasks:

   • Delete a variable by clicking Delete Variable.

   • Delete a match within a variable by clicking the icon.

   • Delete a condition by clicking Delete Condition.

     A rule must have at least one condition.

   • Delete a rule by clicking the icon that appears to the right of the Name option and then clicking Confirm.

4. Click Submit.

To delete a custom rule set

1. Check your Security Application configurations to verify that the desired custom rule is not in use.
2. Navigate to the Custom Rules page.
   1. From the Edgio Developer console, select the desired team space.
   2. From the Security section, click Custom Rules.
3. Click on the desired custom rule set.
4. Click Delete.
5. Click Confirm.