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CCE-99443-4
Description: Lock out users after _n_ unsuccessful consecutive login attempts. - deny= - Number of attempts before the account is locked- unlock_time= - Time in seconds before the account is unlocked Set the lockout number and unlock time to follow local site policy. Rationale: Locking out user IDs ... CCE-99442-6 Description: The Domain Name System (DNS) is a hierarchical naming system that maps names to IP addresses for computers, services and other resources connected to a network. Rationale: Unless a system is specifically designated to act as a DNS server, it is recommended that the package be deleted to ... CCE-99441-8 To configure the system login banner:Edit '/etc/issue.net'. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:'You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use o ... CCE-99440-0 Description: The contents of the `/etc/issue` file are displayed to users prior to login for local terminals.Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing sof ... CCE-95648-2 The contents of the /etc/issue.net file are displayed to users prior to login for remote connections from configured services. Rationale: If the /etc/issue.net file does not have the correct ownership it could be modified by unauthorized users with incorrect or misleading information. Fix ... CCE-95708-4 Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network (127.0.0.0/8).Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loop ... CCE-95651-6 An SSH public key is one of two files used in SSH public key authentication. In this authentication method, a public key is a key that can be used for verifying digital signatures generated using a corresponding private key. Only a public key that corresponds to a private key will be able to authent ... CCE-95674-8 Data from journald may be stored in volatile memory or persisted locally on the server. Logs in memory will be lost upon a system reboot. By persisting logs to local disk on the server they are protected from loss. Rationale: Writing log data to disk will provide the ability to for ... CCE-95697-9 The cron daemon is used to execute batch jobs on the system. Rationale: While there may not be user jobs that need to be run on the system, the system does have maintenance jobs that may include security monitoring that have to run, and cron is used to execute them. Fix: ... CCE-95613-6 The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /tmp. Fix: Run the follow ... CCE-95663-1 While the system administrator can establish secure permissions for users "dot" files, the users can easily override these. Rationale: Group or world-writable user configuration files may enable malicious users to steal or modify other user's data or to gain another us ... CCE-95686-2 Dovecot is an open source mail submission and transport server for Linux based systems. Rationale: Unless mail transport services are to be provided by this system, it is recommended that the service be disabled or deleted to reduce the potential attack surface. Note: Several IMAP ... CCE-95700-1 UsePAM Enables the Pluggable Authentication Module interface. If set to yes this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM account and session module processing for all authentication types. Rationale: When usePAM is set to ye ... CCE-95602-9 Sudo allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user ID is used to determine the user name with which to query the security policy. Rationale: Sudo supports a plugin arch ... CCE-95603-7 Single user mode (rescue mode) is used for recovery when the system detects an issue during boot or by manual selection from the bootloader. Rationale: Requiring authentication in single user mode (rescue mode) prevents an unauthorized user from rebooting the system into single user ... CCE-95649-0 Log files stored in /var/log/ contain logged information from many services on the system, or on log hosts others as well. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected. Fix: Run the ... CCE-95641-7 The contents of the /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Rationale: If the /etc/motd file does not have the correct ownership it could be modified by unauthorized users with incorrect or misleading inform ... CCE-95701-9 The contents of /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization ... CCE-95690-4 The Network File System (NFS) is one of the first and most widely distributed file systems in the UNIX environment. It provides the ability for systems to mount file systems of other servers through the network. The rpcbind service maps Remote Procedure Call (RPC) services to the ports on wh ... CCE-95652-4 The character + in various files used to be markers for systems to insert data from NIS maps at a certain point in a system configuration file. These entries are no longer required on most systems, but may exist in files that have been imported from other platforms. Rationale: ... CCE-95675-5 autofs allows automatic mounting of devices, typically including CD/DVDs and USB drives. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it thems ... CCE-95614-4 The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot run executable binaries from /tmp. Fix: Ru ... CCE-95687-0 HTTP or web servers provide the ability to host web site content. Rationale: Unless there is a need to run the system as a web server, it is recommended that the package be deleted to reduce the potential attack surface. Fix: Run the following command to disable apa ... CCE-95664-9 While the system administrator can establish secure permissions for users .netrc files, the users can easily override these. Rationale: .netrcfiles may contain unencrypted passwords that may be used to attack other systems. Fix: Making global modifications to user ... CCE-95642-5 The contents of the /etc/issue file are displayed to users prior to login for local terminals. Rationale: If the /etc/issue file does not have the correct ownership and permissions it could be modified by unauthorized users with incorrect or misleading information. Fix ... CCE-95653-2 The character + in various files used to be markers for systems to insert data from NIS maps at a certain point in a system configuration file. These entries are no longer required on most systems, but may exist in files that have been imported from other platforms. Rationale: These ... CCE-95676-3 The Samba daemon allows system administrators to configure their Linux systems to share file systems and directories with Windows desktops. Samba will advertise the file systems and directories via the Server Message Block (SMB) protocol. Windows desktop users will be able to mount these directories ... CCE-95638-3 The usermod command can be used to specify which group the root user belongs to. This affects permissions of files that are created by the root user. Rationale: Using GID 0 for the root account helps prevent root-owned files from accidentally becoming accessible to non-privileged users. ... CCE-95680-5 The Common Unix Print System (CUPS) provides the ability to print to both local and network printers. A system running CUPS can also accept print jobs from remote systems and print them to local printers. It also provides a web based remote administration capability. Rationale: If ... CCE-95665-6 chrony is a daemon which implements the Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. Rationale: If chrony is in use on the system proper configuration is vital to ensuring time synchronizat ... CCE-95688-8 Squid is a standard proxy server used in many distributions and environments. Rationale: If there is no need for a proxy server, it is recommended that the squid proxy be deleted to reduce the potential attack surface. Fix: Run the following command to disable HTTP ... CCE-95627-6 A Firewall package should be selected. Most firewall configuration utilities operate as a front end to nftables or iptables. Rationale: A Firewall package is required for firewall management and configuration. Fix: To install a firewall package run: apt ins ... CCE-95643-3 Rsyslog will create logfiles that do not already exist on the system. This setting controls what permissions will be applied to these newly created files. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and p ... CCE-95620-1 Sudo can use a custom log file. Rationale: A sudo log file simplifies auditing of sudo commands. Fix: Edit the file /etc/sudoers or any file in /etc/sudoers.d and add the following : Defaults logfile=<path to custom file> CCE-95692-0 The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system configuration files. The NIS client ( ypbind ) was used to bind a machine to an NIS server and receive the distributed configuration files. Rationale ... CCE-95654-0 The character + in various files used to be markers for systems to insert data from NIS maps at a certain point in a system configuration file. These entries are no longer required on most systems, but may exist in files that have been imported from other platforms. Rationale: These ... CCE-95677-1 The Simple Network Management Protocol (SNMP) server is used to listen for SNMP commands from an SNMP management system, execute the commands or collect the information and then send results back to the requesting system. Rationale: The SNMP server can communicate using SNMP v1, whi ... CCE-95617-7 The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/tmp filesystem is not intended to support devices, set this option to ensure that users cannot attempt to create block or character special devices in /var/tmp. ... CCE-95639-1 AppArmor profiles define what resources applications are able to access. Fix: Run the following command to set all profiles to enforce mode: # aa-enforce /etc/apparmor.d/* Run the following command to set all profiles to complain mode: # aa-complain /etc/apparmor.d/* CCE-95681-3 The Dynamic Host Configuration Protocol (DHCP) is a service that allows machines to be dynamically assigned IP addresses. Rationale: Unless a system is specifically set up to act as a DHCP server, it is recommended that this service be deleted to reduce the potential attack surface. ... CCE-95666-4 Over time, system administration errors and changes can lead to groups being defined in /etc/passwd but not in /etc/group. Rationale: Groups defined in the /etc/passwd file but not in the /etc/group file pose a threat to system security since group permissions are not properly ma ... CCE-95689-6 The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP server, it is recommended that the soft ... CCE-95621-9 AppArmor provides Mandatory Access Controls. Rationale: Without a Mandatory Access Control system installed only the default Discretionary Access Control system will be available. Fix: Run the following command to install apparmor: apt install apparmor apparmor-utils CCE-95644-1 The /etc/gshadow file is used to store the information about groups that is critical to the security of those accounts, such as the hashed password and other security information Rationale: If attackers can gain read access to the /etc/gshadow file, they can easily run a password ... CCE-95670-6 Although the groupadd program will not let you create a duplicate group name, it is possible for an administrator to manually edit the /etc/group file and change the group name. Rationale: If a group is assigned a duplicate group name, it will create and have access to files with t ... CCE-95693-8 All users should have a password change date in the past. Rationale: If a users recorded password change date is in the future then they could bypass any set password expiration. Fix: Investigate any users with a password change date in the future and correct them. ... CCE-95655-7 The shadow group allows system programs which require access the ability to read the /etc/shadow file. No users should be assigned to the shadow group. Rationale: Any users assigned to the shadow group would be granted read access to the /etc/shadow file. If attackers can gain r ... CCE-95618-5 The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /var/tmp. Fix: Run the ... CCE-95632-6 GDM is the GNOME Display Manager which handles graphical login for GNOME based systems. Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system a ... CCE-95682-1 The File Transfer Protocol (FTP) provides networked computers with the ability to transfer files. Rationale: FTP does not protect the confidentiality of data or authentication credentials. It is recommended SFTP be used if file transfer is required. Unless there is a need to run th ... CCE-95667-2 Although the useradd program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually edit the /etc/passwd file and change the UID field. Rationale: Users must be assigned unique UIDs for accountability and to ensure appropriate access prot ... CCE-95645-8 The /etc/passwd file contains user account information that is used by many system utilities and therefore must be readable for these utilities to operate. Rationale: It is critical to ensure that the /etc/passwd file is protected from unauthorized write access. Although it is prote ... CCE-95671-4 nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames. The nftables service reads the /etc/nftables.conf file for a nftables file or files to include in the nftables ruleset. Rationale: A nftables ruleset containing the input, forwa ... CCE-95694-6 The default timeout variable determines the shell timeout for users. The timeout value is measured in seconds. Rationale: Having no timeout value associated with a shell could allow an unauthorized user access to another user's shell session (e.g. user walks away from their computer ... CCE-95656-5 Any account with UID 0 has superuser privileges on the system. Rationale: This access must be limited to only the default root account and only from the system console. Administrative access must be through an unprivileged account using an approved mechanism as noted in Item 5. ... CCE-95619-3 Sudo can be configured to run only from a psuedo-pty. Rationale: Attackers can run a malicious program using sudo which would fork a background process that remains even when the main program has finished executing. Fix: Edit the file /etc/sudoers or any file in /et ... CCE-95679-7 Avahi is a free zeroconf implementation, including a system for multicast DNS/DNS-SD service discovery. Avahi allows programs to publish and discover services and hosts running on a local network with no specific configuration. For example, a user can plug a computer into a network and Avahi automat ... CCE-95610-2 The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Setting this option on a file system prevents users from executing programs from shared memory. This deters users from introducing potentially malicious software on the system. ... CCE-95705-0 A default deny all policy on connections ensures that any unconfigured network usage will be rejected.With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to white list acceptable usage than to black list unacceptable usage. FIX: Make sur ... CCE-95660-7 While no .rhosts files are shipped by default, users can easily create them. Rationale: This action is only meaningful if .rhosts support is permitted in the file /etc/pam.conf . Even though the .rhosts files are ineffective if support is disabled in /etc/pam.conf , they may hav ... CCE-95668-0 Although the groupadd program will not let you create a duplicate Group ID (GID), it is possible for an administrator to manually edit the /etc/group file and change the GID field. Rationale: User groups must be assigned unique GIDs for accountability and to ensure appropriate ... CCE-95683-9 The nftables service allows for the loading of nftables rulesets during boot, or starting of the nftables service. Rationale: The nftables service restores the nftables rules from the rules files referenced in the /etc/sysconfig/nftables.conf file during boot or the starting of the ... CCE-95607-8 The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the user partitions are not intended to support devices, set this option to ensure that users cannot attempt to create block or character special devices. Fix: Run the followin ... CCE-95669-8 Although the useradd program will not let you create a duplicate user name, it is possible for an administrator to manually edit the /etc/passwd file and change the user name. Rationale: If a user is assigned a duplicate user name, it will create and have access to files with the f ... CCE-95600-3 USB storage provides a means to transfer and store files insuring persistence and availability of the files independent of network connection status. Its popularity and utility has led to USB-based malware being a simple and common means for network infiltration and a first step to establishing a pe ... CCE-95706-8 A default deny all policy on connections ensures that any unconfigured network usage will be rejected.With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to white list acceptable usage than to black list unacceptable usage. FIX: Make sur ... CCE-95672-2 Data from journald may be stored in volatile memory or persisted locally on the server. Utilities exist to accept remote export of journald logs, however, use of the rsyslog service provides a consistent means of log collection and export. Rationale: Storing log data on a remote hos ... CCE-95657-3 An account with an empty password field means that anybody may log in as that user without providing a password. Rationale: All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user. Fix: If any accounts in ... CCE-95661-5 The .netrc file contains data for logging into a remote host for file transfers via FTP. Rationale: The .netrc file presents a significant security risk since it stores passwords in unencrypted form. Even if FTP is disabled, user accounts may have brought over .netrc files from ... CCE-95608-6 The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /dev/shm filesystem is not intended to support devices, set this option to ensure that users cannot attempt to create special devices in /dev/shm partitions. Fix: ... CCE-95647-4 The /etc/group file contains a list of all the valid groups defined in the system. The command below allows read/write access for root and read access for everyone else. Rationale: The /etc/group file needs to be protected from unauthorized changes by non-privileged users, but needs ... CCE-95707-6 Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network (127.0.0.0/8).Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loop ... CCE-95673-0 The journald system includes the capability of compressing overly large files to avoid filling up the system with logs or making the logs unmanageably large. Rationale: Uncompressed large files may unexpectedly fill a filesystem leading to resource unavailability. Compressing lo ... CCE-95696-1 Once the rsyslog package is installed it needs to be activated. Rationale: If the rsyslog service is not activated the system may default to the syslogd service or lack logging instead. Fix: Run the following command to enable rsyslog # systemctl --now enable rsyslo ... CCE-95650-8 An SSH private key is one of two files used in SSH public key authentication. In this authentication method, The possession of the private key is proof of identity. Only a private key that corresponds to a public key will be able to authenticate successfully. The private keys need to be stored and h ... CCE-95658-1 Users can be defined in /etc/passwd without a home directory or with a home directory that does not actually exist. Rationale: If the user's home directory does not exist or is unassigned, the user will be placed in "/" and will not be able to write any files or have ... CCE-95612-8 The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /tmp filesystem is not intended to support devices, set this option to ensure that users cannot attempt to create block or character special devices in /tmp. Fix: ... CCE-95659-9 While the system administrator can establish secure permissions for users home directories, the users can easily override these. Rationale: Group or world-writable user home directories may enable malicious users to steal or modify other users data or to gain another user's system ... CCE-95662-3 The .forward file specifies an email address to forward the user's mail to. Rationale: Use of the .forward file poses a security risk in that sensitive data may be inadvertently transferred outside the organization. The .forward file also poses a risk as it can be used to execu ... CCE-95685-4 System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize their clocks to them. Rationale: Time synchronization is important to support time sensi ... CCE-95609-4 The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Setting this option on a file system prevents users from introducing privileged programs onto the system and allowing non-root users to execute them. Fix: Run the following command to remount /dev/shm: # ... CCE-95060-0 The PASS_MIN_DAYS parameter in /etc/login.defs allows an administrator to prevent users from changing their password until a minimum number of days have passed since the last time the user changed their password. It is recommended that PASS_MIN_DAYS parameter be set to 7 or more days. Rationale: By ... CCE-95045-1 In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private a ... CCE-95056-8 The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system configuration files. Rationale: The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor auth ... CCE-95018-8 The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems (similar to cramfs). A squashfs image can be used without having to first decompress the image. Options Explained: disable - would disable the module. disable with error logged - wou ... CCE-95010-5 The /etc/group file contains a list of all the valid groups defined in the system. The command below allows read/write access for root and read access for everyone else. Rationale: The /etc/group file needs to be protected from unauthorized changes by non-privileged users, but needs to be readable ... CCE-95033-7 The talk software makes it possible for users to send and receive messages across systems through a terminal session. Rationale: The software presents a security risk as it uses unencrypted protocols for communication. Fix: Uninstall the talk package: # apt-get purge talk CCE-95071-7 Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure. Rationale: It is still possible for even known gateways to be compromised. Sett ... CCE-95079-0 Mail Transfer Agents (MTA), such as sendmail and Postfix, are used to listen for incoming mail and transfer the messages to the appropriate user or mail server. If the system is not intended to be a mail server, it is recommended that the MTA be configured to only process local mail. Rationale: The ... CCE-99404-6 Description: The commands below set password encryption to `yescrypt` (a much stronger hashing algorithm). All existing accounts will need to perform a password change to upgrade the stored hashes to the new algorithm. Rationale: The yescrypt algorithm provides much stronger hashing than previous av ... CCE-95029-5 Configure /etc/cron.allow and /etc/at.allow to allow specific users to use these services. If /etc/cron.allow or /etc/at.allow do not exist, then /etc/at.deny and /etc/cron.deny are checked. Any user not specifically defined in those files is allowed to use at and cron. By removing the files, only u ... CCE-95006-3 Setting icmp_ignore_bogus_error_responses to 1 prevents the kernel from logging bogus responses (RFC-1122 non-compliant) from broadcast reframes, keeping file systems from filling up with useless log messages. Rationale: Some routers (and some attackers) will send responses that violate RFC-1122 an ... CCE-95044-4 The net.ipv4.ip_forward flag is used to tell the server whether it can forward packets or not. If the server is not to be used as a router, set the flag to 0. Rationale: Setting the flag to 0 ensures that a server with multiple interfaces (for example, a hard proxy), will never be able to forward p ... CCE-95067-5 The freevxfs filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems. Options Explained: disable - would disable the module. disable with error logged - would disable the module and log whenever module is inserted. enable ... CCE-95021-2 The IgnoreRhosts parameter specifies that .rhosts and .shosts files will not be used in RhostsRSAAuthentication or HostbasedAuthentication. Rationale: Setting this parameter forces users to enter a password when authenticating with ssh. Fix: Edit the /etc/ssh/sshd_config file to set the parameter ... CCE-95093-1 The Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on NTP can be found at http://www.ntp.org. NTP can be configured to be a client and/or a server. Rationale: It is recommended that physical ... CCE-95032-9 The file /etc/securetty contains a list of valid terminals that may be logged in directly as root. Rationale: Since the system console has special properties to handle emergency situations, it is important to ensure that the console is in a physically secure location and that unauthorized consoles ... CCE-95047-7 This setting disables the systems ability to accept router advertisements Rationale: It is recommended that systems not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trus ... CCE-95009-7 The /etc/ssh/sshd_config file contains configuration specifications for sshd. The command below sets the owner and group of the file to root. Rationale: The /etc/ssh/sshd_config file needs to be protected from unauthorized changes by non- priliveged users, but needs to be readable as this informati ... CCE-95062-6 Setting net.ipv4.icmp_echo_ignore_broadcasts to 1 will cause the system to ignore all ICMP echo and timestamp requests to broadcast and multicast addresses. Rationale: Accepting ICMP echo and timestamp requests with broadcast or multicast destinations for your network could be used to trick your ho ... CCE-95073-3 The /etc/cron.monthly directory contains system cron jobs that need to run on a monthly basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to us ... CCE-95107-9 This variable limits the types of ciphers that SSH can use during communication. Rationale: Based on research conducted at various institutions, it was determined that the symmetric portion of the SSH Transport Protocol (as described in RFC 4253) has security weaknesses that allowed recovery of up ... CCE-95012-1 The /etc/cron.daily directory contains system cron jobs that need to run on a daily basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user a ... CCE-95035-2 The rsh package contains the client commands for the rsh services. Rationale: These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inad ... CCE-95058-4 When tcp_syncookies is set, the kernel will handle TCP SYN packets normally until the half-open connection queue is full, at which time, the SYN cookie functionality kicks in. SYN cookies work by not using the SYN queue at all. Instead, the kernel simply replies to the SYN with a SYN|ACK, but will i ... CCE-99444-2 Description: Key exchange is any method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages ... CCE-95046-9 The pam_cracklib module checks the strength of passwords. It performs checks such as making sure a password is not a dictionary word, it is a certain length, contains a mix of characters (e.g. alphabet, numeric, other) and more. The following are definitions of the pam_cracklib.so options. * retr ... CCE-95023-8 The PermitRootLogin parameter specifies if the root user can log in using ssh(1). The default is no. Rationale: Disallowing root logins over SSH requires server admins to authenticate using their own individual account, then escalating to root via sudo or su. This in turn limits opportunity for non ... CCE-95069-1 User accounts that have been inactive for over a given period of time can be automatically disabled. It is recommended that accounts that are inactive for 35 or more days be disabled. Rationale: Inactive accounts pose a threat to system security since the users are not logging in to notice failed l ... CCE-95072-5 The INFO parameter specifices that record login and logout activity will be logged. Rationale: SSH provides several logging levels with varying amounts of verbosity. DEBUG is specifically not recommended other than strictly for debugging SSH communications since it provides so much data that it is ... CCE-95019-6 The /etc/crontab file is used by cron to control its own jobs. The commands in this item make sure that root is the user and group owner of the file and that only the owner can access the file. UID - User Identifier is a number assigned by Linux to each user on the system. This number is used to ... CCE-95011-3 In some installations, AIDE is not installed automatically. Rationale: Ensure AIDE is installed to make use of the file integrity features to monitor critical files for changes that could affect the security of the system. CCE-95095-6 This directory contains system cron jobs that need to run on an hourly basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root ... CCE-95034-5 The /etc/passwd file contains user account information that is used by many system utilities and therefore must be readable for these utilities to operate. Rationale: It is critical to ensure that the /etc/passwd file is protected from unauthorized write access. Although it is protected by default, ... CCE-95101-2 The HostbasedAuthentication parameter specifies if authentication is allowed through trusted hosts via the user of .rhosts, or /etc/hosts.equiv, along with successful public key client host authentication. This option only applies to SSH Protocol Version 2. Rationale: Even though the .rhosts files ... CCE-95037-8 The udf filesystem type is the universal disk format used to implement ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is necessary to support writing DVDs and newer optical disc formats. Optio ... CCE-95052-7 Setting net.ipv4.conf.all.rp_filter and net.ipv4.conf.default.rp_filter to 1 forces the Linux kernel to utilize reverse path filtering on a received packet to determine if the packet was valid. Essentially, with reverse path filtering, if the return packet does not go out the same interface that the ... CCE-95075-8 ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt ... CCE-95100-4 SSH supports two different and incompatible protocols: SSH1 and SSH2. SSH1 was the original protocol and was subject to security issues. SSH2 is more advanced and secure. Rationale: SSH v1 suffers from insecurities that do not affect SSH v2. Fix: Edit the /etc/ssh/sshd_config file to set the param ... CCE-95040-2 The rsyslog package is a third party package that provides many enhancements to syslog, such as multi-threading, TCP communication, message filtering and data base support. Rationale: The security enhancements of rsyslog such as connection-oriented (i.e. TCP) transmission of logs, the option to log ... CCE-99400-4 Description: The two options `ClientAliveInterval` and `ClientAliveCountMax` control the timeout of ssh sessions. When the `ClientAliveInterval` variable is set, ssh sessions that have no activity for the specified length of time are terminated. When the `ClientAliveCountMax` variable is set, `sshd` ... CCE-95025-3 There are a number of accounts provided with Ubuntu that are used to manage applications and are not intended to provide an interactive shell. Rationale: It is important to make sure that accounts that are not being used by regular users are locked to prevent them from being used to provide an inte ... CCE-95074-1 The PermitUserEnvironment option allows users to present environment options to the ssh daemon. Rationale: Permitting users the ability to set environment variables through the SSH daemon could potentially allow users to bypass security controls (e.g. setting an execution path that has ssh executin ... CCE-95013-9 The hfsplus filesystem type is a hierarchical filesystem designed to replace hfs that allows you to mount Mac OS filesystems. Options Explained: disable - would disable the module. disable with error logged - would disable the module and log whenever module is inserted. enable - would ena ... CCE-95081-6 The hfs filesystem type is a hierarchical filesystem that allows you to mount Mac OS filesystems. Options Explained: disable - would disable the module. disable with error logged - would disable the module and log whenever module is inserted. enable - would enable the module. Rationale: ... CCE-95103-8 The su command allows a user to run a command or shell as another user. The program has been superseded by sudo, which allows for more granular control over privileged access. Normally, the su command can be executed by any user. By uncommenting the pam_wheel.so statement in /etc/pam.d/su, the su co ... CCE-99403-8 Description: The `/etc/security/opasswd` file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords. Rationale: Forcing users not to reuse their past 24 passwords make it less likely that an attacker will be able to guess the password.Note that th ... CCE-95005-5 The rsyslog utility supports the ability to send logs it gathers to a remote log host running syslogd(8) or to receive messages from remote hosts, reducing administrative overhead. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root acce ... CCE-95089-9 The PASS_MAX_DAYS parameter in /etc/login.defs allows an administrator to force passwords to expire once they reach a defined age. It is recommended that the PASS_MAX_DAYS parameter be set to less than or equal to 60 days. Rationale: The window of opportunity for an attacker to leverage compromised ... CCE-95028-7 The /etc/shadow file is used to store the information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking pro ... CCE-95066-7 There are several options available to limit which users and group can access the system via SSH. It is recommended that at least one of the following options be leveraged: AllowUsers The AllowUsers variable gives the system administrator the option of allowing specific users to ssh into the system. ... CCE-95043-6 By default, rsyslog does not listen for log messages coming in from remote systems. The ModLoad tells rsyslog to load the imtcp.so module so it can listen over a network via TCP. The InputTCPServerRun option instructs rsyslogd to listen on the specified TCP port. Rationale: The guidance in the sect ... CCE-95039-4 The PASS_WARN_AGE parameter in /etc/login.defs allows an administrator to notify users that their password will expire in a defined number of days. It is recommended that the PASS_WARN_AGE parameter be set to 7 or more days. Rationale: Providing an advance warning that a password will be expiring g ... CCE-95077-4 The /etc/cron.weekly directory contains system cron jobs that need to run on a weekly basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user ... CCE-95080-8 The Banner parameter specifies a file whose contents must be sent to the remote user before authentication is permitted. By default, no banner is displayed. Rationale: Banners are used to warn connecting users of the particular sites policy regarding connection. Consult with your legal department f ... CCE-95004-8 The system includes the capability of rotating log files regularly to avoid filling up the system with logs or making the logs unmanageable large. The file /etc/logrotate.d/rsyslog is the configuration file used to rotate log files created by rsyslog. Rationale: By keeping the log files smaller and ... CCE-95027-9 IPtables is an application that allows a system administrator to configure the IPv4 tables, chains and rules provided by the Linux kernel firewall. ufw was developed to ease IPtables firewall configuration. Rationale: IPtables provides extra protection for the Linux system by limiting communicatio ... CCE-95088-1 The MaxAuthTries parameter specifies the maximum number of authentication attempts permitted per connection. When the login failure count reaches half the number, error messages will be written to the syslog file detailing the login failure. Rationale: Setting the MaxAuthTries parameter to a low nu ... CCE-95042-8 The default umask determines the permissions of files created by users. The user creating the file has the discretion of making their files and directories readable by others via the chmod command. Users who wish to allow their files and directories to be readable by others by default may choose a d ... CCE-95030-3 This setting prevents the system from accepting ICMP redirects. ICMP redirects tell the system about alternate routes for sending traffic. Rationale: It is recommended that systems not accept ICMP redirects as they could be tricked into routing traffic to compromised machines. Setting hard routes w ... CCE-95038-6 The prelinking feature changes binaries in an attempt to decrease their startup time. Rationale: The prelinking feature can interfere with the operation of AIDE, because it changes binaries. Prelinking can also increase the vulnerability of the system if a malicious user is able to compromise a com ... CCE-95053-5 The PermitEmptyPasswords parameter specifies if the server allows login to accounts with empty password strings. Rationale: Disallowing remote shell access to accounts that have an empty password reduces the probability of unauthorized access to the system Fix: Edit the /etc/ssh/sshd_config file t ... CCE-95099-8 The X Window system provides a Graphical User Interface (GUI) where users can have multiple windows in which to run programs and various add on. The X Window system is typically used on desktops where users login, but not on servers where users typically do not login. Note: The patch can lead to log ... CCE-95092-3 A core dump is the memory of an executable program. It is generally used to determine why a program aborted. It can also be used to glean confidential information from a core file. The system provides the ability to set a soft limit for core dumps, but this can be overridden by the user. Rationale: ... CCE-95625-0 The telnet package contains the telnet client, which allows users to start connections to other systems via the telnet protocol. Rationale: The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal crede ... CCE-95626-8 The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP client, it is recommended that the softwa ... CCE-95678-9 The rsyncd service can be used to synchronize files between systems over network links. Rationale: The rsyncd service presents a security risk as it uses unencrypted protocols for communication. Fix: Run the following command to disable rsync # systemctl --now disa ... CCE-95623-5 The eXtended InterNET Daemon ( xinetd ) is an open source super daemon that replaced the original inetd daemon. The xinetd daemon listens for well known services and dispatches the appropriate daemon to properly respond to service requests. Rationale: If there are no xinetd service ... CCE-95624-3 The inetd daemon listens for well known services and dispatches the appropriate daemon to properly respond to service requests. Rationale: If there are no inetd services required, it is recommended that the daemon be removed. Fix: Run the following command to uninstall openbsd-i ... |
