Blocking Commonly Exploited Area Codes

When blocking commonly exploited area codes, create a unique route pattern for each area code that you want to block. You can create different restriction levels; for example, general employees are not allowed to call these numbers, but executives and managers are allowed to. Use different route filters, partitions, and calling search spaces to generate restriction levels. As a general recommendation to prevent toll fraud, you should block as many numbers as possible. For the example shown in Figure 22-4, all calls to the Bahamas are blocked. For each number that you want to block, create a route pattern that explicitly blocks the number. Often, the decision as to whether a number should be blocked or allowed depends on company policies or simply on whether it is necessary to call the number.

Figure 22-4. Restricting Specific Area Codes

Table 22-1 shows some of the most commonly exploited area codes that you might want to block. It is not an exhaustive list, and some of these area codes might not apply to your organization.

Table 22-1. Commonly Exploited North American Area Codes

Country	Area Code	Blocked Cisco CallManager Pattern
Anguilla	264	9.1264xxxxxxx
Antigua/ Barbuda	268	9.1268xxxxxxx
Bahamas	242	9.1242xxxxxxx
Barbados	246	9.1246xxxxxxx
Bermuda	441	9.1441xxxxxxx
British Virgin Islands	284	9.1284xxxxxxx
Cayman Islands	345	9.1345xxxxxxx
Dominica	767	9.1767xxxxxxx
Dominican Republic	809	9.1809xxxxxxx
Grenada	473	9.1473xxxxxxx
Jamaica	876	9.1876xxxxxxx
Montserrat	664	9.1664xxxxxxx
Puerto Rico	787	9.1787xxxxxxx
St. Kitts & Nevis	869	9.1869xxxxxxx
St. Lucia	758	9.1758xxxxxxx
St. Vincent & the Grenadines	784	9.1784xxxxxxx
Toll Charge	900 976	9.1900xxxxxxx 9.1976xxxxxxx
Trinidad & Tobago	868	9.1868xxxxxxx
Turks & Caicos Islands	649	9.1649xxxxxxx
U.S. Virgin Islands	340	9.1242xxxxxxx

In the worldwide country code numbering scheme, several countries do not use their own country codes.

These numbers have the same format as the NANP[access code] [area code] [number] (for example, 9.142xxxxxxx)but a call to one of these destinations results in an international toll charge.

Administrators should make sure that all of the devices in the IP telephony network can reach only the destinations that they should be able to reach. For example, a lobby phone should not be able to call international numbers. In situations in which individuals in your organization have legitimate business in one of these countries, the recommendation is to explicitly configure route patterns that will match those businesses, while still blocking the area code as a whole.