Cisco IOS XE Switch NDM Security Technical Implementation Guide

Network devices are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the network device must support the organizational requirements providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved. Some network devices have capabilities enabled by default; if these capabilities are not necessary, they must be disabled. If a particular capability is used, then it must be documented and approved.

Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Network devices must enforce cryptographic representations of passwords when storing passwords in databases, configuration files, and log files. Passwords must be protected at all times; using a strong one-way hashing encryption algorithm with a salt is the standard method for providing a means to validate a password without having to store the actual password. Performance and time required to access are factors that must be considered, and the one way hash is the most feasible means of securing the password and providing an acceptable measure of password security. If passwords are stored in clear text, they can be plainly read and easily compromised. In many instances, verifying the user knows a password is performed using a password verifier. In its simplest form, a password verifier is a computational function that is capable of creating a hash of a password and determining if the value provided by the user matches the stored hash.

Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session will also free up resources committed by the managed network element. Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at the operating system level, or de-allocating networking assignments at the application level if multiple application sessions are using a single, operating system-level network connection. This does not mean that the device terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DoD data may be compromised. Nonlocal maintenance and diagnostic activities are those activities conducted by individuals communicating through a network, either an external network (e.g., the Internet) or an internal network. Currently, HMAC is the only FIPS-approved algorithm for generating and verifying message/data authentication codes in accordance with FIPS 198-1. Products that are FIPS 140-2 validated will have an HMAC that meets specification; however, the option must be configured for use as the only message authentication code used for authentication to cryptographic modules. Separate requirements for configuring applications and protocols used by each application (e.g., SNMPv3, SSHv2, NTP, HTTPS, and other protocols and applications that require server/client authentication) are required to implement this requirement. Where SSH is used, the SSHv2 protocol suite is required because it includes Layer 7 protocols such as SCP and SFTP, which can be used for secure file transfers.

This requires the use of secure protocols instead of their unsecured counterparts, such as SSH instead of telnet, SCP instead of FTP, and HTTPS instead of HTTP. If unsecured protocols (lacking cryptographic mechanisms) are used for sessions, the contents of those sessions will be susceptible to eavesdropping, potentially putting sensitive data (including administrator passwords) at risk of compromise and potentially allowing hijacking of maintenance sessions.

Centralized management of user accounts and authentication increases the administrative access to the switch. This control is a particularly important protection against the insider threat. With robust centralized management, audit records for administrator account access to the organization's network devices can be more readily analyzed for trends and anomalies. The alternative method of defining administrator accounts on each device exposes the device configuration to remote access authentication attacks and system administrators with multiple authenticators for each network device.

The aggregation of log data kept on a syslog server can be used to detect attacks and trigger an alert to the appropriate security personnel. The stored log data can used to detect weaknesses in security that enable the network IA team to find and address these weaknesses before breaches can occur. Reviewing these logs, whether before or after a security breach, are important in showing whether someone is an internal employee or an outside threat.

Network devices running an unsupported operating system lack current security fixes required to mitigate the risks associated with recent vulnerabilities. Running a supported release also enables operations to maintain a stable and reliable network provided by improved quality of service and security features.