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Oracle SBC Security Guide

Appendix G: Blacklisting with Local Routing Tables

Several industry groups such as the GSMA Fraud Forum and the Communications Fraud Control

Association (CFCA) track phone numbers and number prefixes that have been verified as participating in

various types of fraud. These numbers are published as a list for their members. Many organizations also

track numbers that abuse their network on a regular basis.

While it can be more of an art than a science, some customers wish to blacklist incoming or outgoing calls

based on a dialed number prefix, or the entire dialed number. While complex or expensive fraud

management solutions can be used, this Appendix provides a simple way to perform this blacklisting on

the SBC.

WARNING: This procedure will end up denying calls coming into your network. Be sure to test your

local route tables (LRT) in a test environment before deploying in production.

It is assumed that as calls have been sent to the SBC or as they enter the SBC that they will be

“normalized” by either the directly connected agent or an incoming HMR to match the local dial plan. For

example in North America it is necessary to include the leading “1” for NANP and remove the “011” for

calls outside of the NANP. If this is not possible, then the “011” can be pre-pended onto the number

matches in the LRT file.

Depending on what you are trying to prevent, you may want to check both the FROM and TO fields in

SIP messages. This same strategy can be used on your access realm, or even your core realm if you so

choose.

To create the blacklist for routing you need to:

1. Enter your FROM or TO blacklist numbers into one or more LRTs - and save them with an

“.xml” extension. Next gzip them (.gz format). A sample LRT format is found below.

2. Upload the .xml.gz file to the to SBC in the /code/lrt directory (which will need to be created the

first time)

3. Update SBC config as depicted below

Apply an LRT check for the SIP From and To headers as the first two policy-attributes on all incoming

realms, and on the core side if you want to detect outgoing fraudulent calls.

local-policy

from-address

to-address

source-realm

access

description

activate-time N/A

deactivate-time N/A

state enabled

policy-priority none

last-modified-by [email protected]

last-modified-date 2012-10-26 17:13:15

(The first policy checks the FROM field. Note that the .xml.gz file extension is not specified.)

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