One of the most important steps in securing an IP telephony server is installing all the applicable product or component security updates and then making sure that they are kept up to date. Cisco provides three types of updates for the Cisco IP Telephony Operating System:
An IP telephony server must be used for IP telephony purposes only. The server should not be used as a common file server that stores user data or has user applications, such as Microsoft Office products, installed on it. File-share access has to be limited to the absolute minimum needed (for instance, to access log files and generate reports). Strict file access control has to be deployed, and auditing of network file access should be enabled. This practice also eliminates the need to add user accounts to the server; only administrator and auditor accounts should exist. If network file access is not needed at all, it should be disabled to enhance the security of the server.
The more services that are running on a server, the more likely it is that vulnerabilities can be exploited by an attacker. To minimize this risk, only the services that are needed should be activated. Many services that are not needed have already been disabled in the Cisco hardened version of the Microsoft Windows 2000 Server operating system.
To make Cisco CallManager even more secure, Cisco provides additional security scripts and information on how to protect the Cisco IP Telephony Operating System against common threats.
Do not install any other application on the servers unless it is approved software, such as Cisco Security Agent or antivirus products. A hardened IP telephony server has to be stripped down to run only the services and applications that are needed for its operation.
IP Telephony Operating System Security Scripts
Cisco IP Telephony Operating System 2.6 and later includes scripts and information guides on additional security settings. These security guides and scripts provide additional security settings beyond those that are installed by default in the Cisco IP Telephony Operating System. The settings in the optional security script have not been included by default and are not intended for all customers to use. When planning to use the optional security script, consider these points:
Applying the optional security script can destroy collocated applications, such as Cisco IPCC Express, Cisco IP IVR, and Cisco IP Queue Manager (IP QM)!
As shown in Figure 20-2, the optional security script and some additional information are available in the C:utilsSecurityTemplates folder.
Figure 20-2. CallManager Security Script Templates
The script file is a batch job that can be started by clicking the CCM-OS-OptionalSecurity.cmd file. Before doing so, read the CCM-OS-OptionalSecurity-Readme.htm file to identify possible issues with applications running on the operating system:
In addition, Cisco has provided an additional security script in the C:utils directory, shown in Figure 20-3. This script is called the IP security filter and will block the fixed Windows 2000 and SQL ports. Read the IPSec-W2KSQL-Readme.htm file for instructions on how to use the IP security filter.
Figure 20-3. CallManager SQL Security Script Template
The security script provides the following benefits:
The name of the IPSec-W2kSQL file has nothing to do with the IPsec virtual private network (VPN) umbrella standard.
To secure the access to file shares, limit access to the absolute minimum number of users who need it, as shown in Figure 20-4. Check the share permissions on all shared folders, for example, the CDR and TFTPPath folders. Avoid assigning share permissions for the Everyone group. You can find detailed information on how to secure file shares in the CCM-OS-OptionalSecurity-Readme guide, located in the folder C:UtilsSecurityTemplates.
Figure 20-4. Managing CallManager Share Permissions
Part I: Cisco CallManager Fundamentals
Introduction to Cisco Unified Communications and Cisco Unified CallManager
Cisco Unified CallManager Clustering and Deployment Options
Cisco Unified CallManager Installation and Upgrades
Part II: IPT Devices and Users
Cisco IP Phones and Other User Devices
Configuring Cisco Unified CallManager to Support IP Phones
Cisco IP Telephony Users
Cisco Bulk Administration Tool
Part III: IPT Network Integration and Route Plan
Cisco Catalyst Switches
Configuring Cisco Gateways and Trunks
Cisco Unified CallManager Route Plan Basics
Cisco Unified CallManager Advanced Route Plans
Configuring Hunt Groups and Call Coverage
Implementing Telephony Call Restrictions and Control
Implementing Multiple-Site Deployments
Part IV: VoIP Features
Configuring User Features, Part 1
Configuring User Features, Part 2
Configuring Cisco Unified CallManager Attendant Console
Configuring Cisco IP Manager Assistant
Part V: IPT Security
Securing the Windows Operating System
Securing Cisco Unified CallManager Administration
Preventing Toll Fraud
Hardening the IP Phone
Understanding Cryptographic Fundamentals
Understanding the Public Key Infrastructure
Understanding Cisco IP Telephony Authentication and Encryption Fundamentals
Configuring Cisco IP Telephony Authentication and Encryption
Part VI: IP Video
Introducing IP Video Telephony
Configuring Cisco VT Advantage
Part VII: IPT Management
Introducing Database Tools and Cisco Unified CallManager Serviceability
Configuring Alarms and Traces
Using Additional Management and Monitoring Tools
Part VIII: Appendix
Appendix A. Answers to Review Questions