Restricting the use of nonessential software (programs) includes restricting the roles allowed to approve program execution; prohibiting auto-execute; program blacklisting and whitelisting; or restricting the number of program instances executed at the same time. The organization makes a security-based determination which functions, ports, protocols, and/or services are restricted. Bluetooth, File Transfer Protocol (FTP), and peer-to-peer networking are examples of protocols organizations consider preventing the use of, restricting, or disabling.

The process used to identify software programs that are not authorized to execute on systems is commonly referred to as blacklisting. The process used to identify software programs that are authorized to execute on systems is commonly referred to as whitelisting. Whitelisting is the stronger of the two policies for restricting software program execution. In addition to whitelisting, organizations consider verifying the integrity of whitelisted software programs using, for example, cryptographic checksums, digital signatures, or hash functions. Verification of whitelisted software can occur either prior to execution or at system startup. [SP 800-167] provides guidance on application whitelisting.

Users can install software in organizational systems if provided the necessary privileges. To maintain control over the software installed, organizations identify permitted and prohibited actions regarding software installation through policies. Permitted software installations include updates and security patches to existing software and applications from organization-approved “app stores.” Prohibited software installations may include software with unknown or suspect pedigrees or software that organizations consider potentially malicious. The policies organizations select governing user-installed software may be organization-developed or provided by some external entity. Policy enforcement methods include procedural methods, automated methods, or both.

Common device identifiers include Media Access Control (MAC), Internet Protocol (IP) addresses, or device-unique token identifiers. Management of individual identifiers is not applicable to shared system accounts. Typically, individual identifiers are the user names associated with the system accounts assigned to those individuals. Organizations may require unique identification of individuals in group accounts or for detailed accountability of individual activity. In addition, this requirement addresses individual identifiers that are not necessarily associated with system accounts. Organizational devices requiring identification may be defined by type, by device, or by a combination of type/device. [SP 800-63-3] provides guidance on digital identities.

Individual authenticators include the following: passwords, key cards, cryptographic devices, and one-time password devices. Initial authenticator content is the actual content of the authenticator, for example, the initial password. In contrast, the requirements about authenticator content include the minimum password length. Developers ship system components with factory default authentication credentials to allow for initial installation and configuration. Default authentication credentials are often well known, easily discoverable, and present a significant security risk. Systems support authenticator management by organization-defined settings and restrictions for various authenticator characteristics including minimum password length, validation time window for time synchronous one-time tokens, and number of allowed rejections during the verification stage of biometric authentication. Authenticator management includes issuing and revoking, when no longer needed, authenticators for temporary access such as that required for remote maintenance. Device authenticators include certificates and passwords. [SP 800-63-3] provides guidance on digital identities.

Multifactor authentication requires the use of two or more different factors to authenticate. The factors are defined as something you know (e.g., password, personal identification number [PIN]); something you have (e.g., cryptographic identification device, token); or something you are (e.g., biometric). Multifactor authentication solutions that feature physical authenticators include hardware authenticators providing time-based or challenge-response authenticators and smart cards. In addition to authenticating users at the system level (i.e., at logon), organizations may also employ authentication mechanisms at the application level, when necessary, to provide increased information security. Access to organizational systems is defined as local access or network access. Local access is any access to organizational systems by users (or processes acting on behalf of users) where such access is obtained by direct connections without the use of networks. Network access is access to systems by users (or processes acting on behalf of users) where such access is obtained through network connections (i.e., nonlocal accesses). Remote access is a type of network access that involves communication through external networks. The use of encrypted virtual private networks for connections between organization-controlled and non-organization controlled endpoints may be treated as internal networks with regard to protecting the confidentiality of information. [SP 800-63-3] provides guidance on digital identities. [24] Multifactor authentication requires two or more different factors to achieve authentication. The factors include: something you know (e.g., password/PIN); something you have (e.g., cryptographic identification device, token); or something you are (e.g., biometric). The requirement for multifactor authentication should not be interpreted as requiring federal Personal Identity Verification (PIV) card or Department of Defense Common Access Card (CAC)-like solutions. A variety of multifactor solutions (including those with replay resistance) using tokens and biometrics are commercially available. Such solutions may employ hard tokens (e.g., smartcards, key fobs, or dongles) or soft tokens to store user credentials. [25] Local access is any access to a system by a user (or process acting on behalf of a user) communicating through a direct connection without the use of a network. Network access is any access to a system by a user (or a process acting on behalf of a user) communicating through a network (e.g., local area network, wide area network, Internet).

Authentication processes resist replay attacks if it is impractical to successfully authenticate by recording or replaying previous authentication messages. Replay-resistant techniques include protocols that use nonces or challenges such as time synchronous or challenge-response one-time authenticators. [SP 800-63-3] provides guidance on digital identities.

Identifiers are provided for users, processes acting on behalf of users, or devices (3.5.1). Preventing reuse of identifiers implies preventing the assignment of previously used individual, group, role, or device identifiers to different individuals, groups, roles, or devices.

Inactive identifiers pose a risk to organizational information because attackers may exploit an inactive identifier to gain undetected access to organizational devices. The owners of the inactive accounts may not notice if unauthorized access to the account has been obtained.

This requirement applies to single-factor authentication of individuals using passwords as individual or group authenticators, and in a similar manner, when passwords are used as part of multifactor authenticators. The number of changed characters refers to the number of changes required with respect to the total number of positions in the current password. To mitigate certain brute force attacks against passwords, organizations may also consider salting passwords.