The Login Password Retry Lockout feature, added in Cisco IOS Software Release 12.3(14)T, allows you to lock out a local user account after a configured number of unsuccessful login attempts. Make sure that your mongod and mongos instances are only accessible on trusted networks. In some situations, it might be possible for an attacker to cause the Cisco IOS device to send many ICMP redirect messages, which results in an elevated CPU load. It is for this reason that devices need to be hardened against DoS attacks that utilize a high rate of IP packets that are due to expire. This prevents both the elevated CPU load and possible subversion of security controls that IP options can enable. It is recommended to add a loopback interface to each device as a management interface and that it be used exclusively for the management plane. Refer to ACL IP Options Selective Drop for more information about this feature. After MPP is enabled, no interfaces except designated management interfaces accept network management traffic that is destined to the device. ⢠Use the proper case for each letter, just as it appears in the phrase. In Cisco IOS Software Release 12.4(15)T and later, the Reserve Memory for Console Access feature can be used in order to reserve enough memory to ensure console access to a Cisco IOS device for administrative and troubleshooting purposes. Filtering with an interface access list elicits the transmission of ICMP unreachable messages back to the source of the filtered traffic. The ACL below includes comprehensive filtering of IP fragments. The use of this command is illustrated as follows: Refer to Neighbor Router Authentication for more information about BGP peer authentication with MD5. The use of buffered logging is highly recommended versus logging to either the console or monitor sessions. Port Security is used in order to mitigate MAC address spoofing at the access interface. If transit traffic can cause a device to process switch traffic, the control plane of a device can be affected which may lead to an operational disruption. Configured prefix lists limit the prefixes that are sent or received to those specifically permitted by the routing policy of a network. Hence, the user is authenticated or denied access based on the encrypted signature. The use of Transit ACLs is also relevant to the hardening of the data plane. In this overview, protection of the management, control, and data planes is discussed, and recommendations for configuration are supplied. CPPr divides the aggregate control plane into three separate control plane categories known as subinterfaces: Host, Transit, and CEF-Exception subinterfaces exist. Filtering packets based on TTL values can also be used in order to ensure that the TTL value is not lower than the diameter of the network, thus protecting the control plane of downstream infrastructure devices from TTL expiry attacks. ICMP unreachable rate limiting can be changed from the default with the global configuration command ip icmp rate-limit unreachable interval-in-ms. Proxy ARP is the technique in which one device, usually a router, answers ARP requests that are intended for another device. Administrators are advised to evaluate each option for its potential risk before they implement the option. Refer to Memory Threshold Notifications for more information about this feature. In many cases, you can disable the reception and transmission of certain types of messages on an interface in order to minimize the amount of CPU load that is required to process unneeded packets. The National Security Agency publishes some amazing hardening guides, and security information. In other words, ICMP redirects should never go beyond a Layer 3 boundary. The repository that you use in order to archive Cisco IOS device configurations needs to be secured. This command verifies the integrity of image c3900-universalk9-mz.SSA in flash with the keys in the device key store: The Digitally Signed Cisco Software feature was also integrated in Cisco IOS XE Release 3.1.0.SG for the Cisco Catalyst 4500 E-Series Switches. This CoPP policy drops transit packets that are received by a device when any IP options are present: This CoPP policy drops transit packets received by a device when these IP options are present: In the preceding CoPP policies, the access control list entries (ACEs) that match packets with the permit action result in these packets being discarded by the policy-map drop function, while packets that match the deny action (not shown) are not affected by the policy-map drop function. The ACL counters can be cleared by with the clear ip access-list counters acl-name EXEC command. Memory Leak Detector is able to find leaks in all memory pools, packet buffers, and chunks. Examples of packets that are classified for the host subinterface category include management traffic such as SSH or Telnet and routing protocols. Refer to Flexible Packet Matching, located on the Cisco IOS Flexible Packet Matching homepage, for more information about the feature. Specifically, portions of the IP and TCP headers, TCP payload, and a secret key are used in order to generate the digest. The result is that you are able to use a MAC access list on the IP environment. If SSH is enabled, it is recommended to disable SSHv1 by using the ip ssh version 2 command. This scenario is common in a publicly accessible network or anywhere that servers provide content to untrusted clients. A vty and tty should be configured in order to accept only encrypted and secure remote access management connections to the device or through the device if it is used as a console server. As, LAN hardening is done to secure whole organization network from attacks. This example configuration enables AAA command accounting for EXEC commands entered at privilege levels zero, one, and 15. The starting value varies by operating system and typically ranges from 64 to 255. Regardless of whether flow information is exported to a remote collector, you are advised to configure network devices for NetFlow so that it can be used reactively if needed. Firewalls are the first line of defense for any network thatâs connected to the Internet. This example illustrates configuration of this feature: Refer to Understanding Unicast Reverse Path Forwarding for more information about the configuration and use of Unicast RPF. Private VLANs (PVLANs) are a Layer 2 security feature that limits connectivity between workstations or servers within a VLAN. These management users can access the IOS device via SSH, HTTPS, telnet, or HTTP. Insecure access to this information can undermine the security of the entire network. In Cisco IOS Software Release 12.3(4)T and later, you can use the ACL Support for the Filtering IP Options feature in a named, extended IP access list in order to filter IP packets with IP options present. There are two security concerns presented by IP options. This document describes the information to help you secure your Cisco IOS ® system devices, which increases the overall security of your network. DISA releases new STIGs at least once every quarter. These services include: Although abuse of the small services can be avoided or made less dangerous by anti-spoofing access lists, the services must be disabled on any device accessible within the network. Additionally, a malicious user can create a denial of service (DoS) condition with repeated attempts to authenticate with a valid username. These commands add the new special key to the key store from the current production image, copy a new ROMMON image (C3900_rom-monitor.srec.SSB) to the storage area (usbflash0:), upgrade the ROMMON file, and revoke the old special key: A new special image (c3900-universalk9-mz.SSB) can then be copied to the flash to be loaded and the signature of the image is verified with the newly added special key (.SSB): Key revocation and replacement is not supported on Catalyst 4500 E-Series Switches that run Cisco IOS XE Software, although these switches do support the Digitally Signed Cisco Software feature. Prefixes that are sourced from all other autonomous systems are filtered and not installed in the routing table. A firewall is a security-conscious router that sits between your network and the outside world and prevents Internet users from wandering into your LAN and messing around. Structured around the three planes into which functions of a network device can be categorized, this document provides an overview of each included feature and references to related documentation. The rACL protects the device from harmful traffic before the traffic impacts the route processor. There are many tools available that can easily decrypt these passwords. Cisco IOS software provides several flexible logging options that can help achieve the network management and visibility goals of an organization. The small services are disabled by default in Cisco IOS Software Releases 12.0 and later. This causes non-initial fragments to be evaluated solely on the Layer 3 portion of any configured ACE. All rights reserved. An iACL is constructed and applied in order to specify connections from hosts or networks that need to be allowed to network devices. This directed broadcast functionality has been leveraged as an amplification and reflection aid in several attacks, including the smurf attack. Active Directory plays a critical role in the IT infrastructure, and ensures the harmony and security of different network resources in a global, interconnected environment. This example uses an extended named access list that illustrates the configuration of this feature: This example demonstrates the use of a VLAN map in order to deny TCP ports 139 and 445 as well as the vines-ip protocol: Refer to Configuring Network Security with ACLs for more information about the configuration of VLAN maps. A security configuration checklist (also called a lockdown, hardening guide, or benchmark) is a series of instructions or procedures for configuring an IT product to a particular operational environment, for verifying that the product has been configured properly, and/or for identifying unauthorized changes to the product. Firewalls are the first line of defense for any network that’s connected to the Internet. Refer to PFC3 Hardware-based Rate Limiter Default Settings for more information. This example uses an extended named access list in order to illustrate the configuration of this feature: Refer to the Port ACL section of Configuring Network Security with ACLs for more information about the configuration of PACLs. In addition, CPPr includes these control plane protection features: Refer to Control Plane Protection and Understanding Control Plane Protection (CPPr) for more information on the configuration and use of the CPPr feature. Hardening approach. This configuration example shows the use of these commands: Refer to Cisco IOS Network Management Command Reference for more information about global configuration commands. This allows for a locally defined user to be created for one or more network administrators. When you revoke a special key, a production image is loaded. The coverage of security features in this document often provides enough detail for you to configure the feature. More information about this feature is available in the Traffic Identification and Traceback section of this document and at http://www.cisco.com/go/netflow (registered customers only) . The information sent to the TACACS+ server includes the command executed, the date it was executed, and the username of the user who enters the command. This document describes the information to help you secure your Cisco IOS® system devices, which increases the overall security of your network. Unicast RPF can be configured in one of two modes: loose or strict. DAI intercepts and validates the IP-to-MAC address relationship of all ARP packets on untrusted ports. In order to propagate the no vstack command into the network, use one of these methods: In order to enable the Smart Install client functionality later, enter the vstack command on all client switches either manually or with a script. Additionally, NetFlow can be implemented with collectors that can provide long-term trending and automated analysis. Protection is provided in various layers and is often referred to as defense in depth. The operational procedures in use on the network contribute as much to security as the configuration of the underlying devices. Should a single server become compromised, the lack of connectivity to other servers due to the application of PVLANs might help limit the compromise to the one server. EIGRP and RIPv2 utilize Key Chains as part of the configuration. CoPP is available in Cisco IOS Software Release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T. DISA has released the Red Hat Enterprise Linux 8 Security Technical Implementation Guide (STIG). BGP is often targeted by attackers because of its ubiquity and the set and forget nature of BGP configurations in smaller organizations. Messages saved on an ATA drive persist after a router is rebooted. Some feature descriptions in this document were written by Cisco information development teams. This includes interfaces that connect to other organizations, remote access segments, user segments, and segments in data centers. Notice that any unauthorized use of the system is unlawful and can be subject to civil and criminal penalties. This configuration example includes the configuration of a logging buffer of 16384 bytes, as well as a severity of 6, informational, which indicates that messages at levels 0 (emergencies) through 6 (informational) is stored: Refer to Cisco IOS Network Management Command Reference for more information about buffered logging. In some legal jurisdictions, it can be impossible to prosecute and illegal to monitor malicious users unless they have been notified that they are not permitted to use the system. Only special and production keys can be revoked in the event of a key compromise. This is possible with the use of an access control list as an option to the ip directed-broadcast command. Note that authorized users can lock themselves out of a device if the number of unsuccessful login attempts is reached. If there are no protocols in use that require IP options, ACL IP Options Selective Drop is the preferred method to drop these packets. For buffered logging, the logging buffered level command is used. Often an attacker uses ARP poisoning in order to perform a man-in-the-middle attack. Layer 3 filtering with a Router ACL or firewall can prevent the subversion of the PVLAN configuration. Refer to Private VLANs (PVLANs) - Promiscuous, Isolated, Community, located on the LAN Security homepage, for more information about the use and configuration of Private VLANs. NetFlow and Classification ACLs are the two primary methods to accomplish this with Cisco IOS software. Refer to TTL Expiry Attack Identification and Mitigation for more information on mitigating TTL expiry-based attacks. This number represents the percentage of the maximum prefixes value at which point a log message is sent. This ensures that the device on the remote end of the connection is still accessible and that half-open or orphaned connections are removed from the local Cisco IOS device. This checklist is a collection of all the hardening steps that are presented in this guide. This information is designed in order to corrupt the ARP cache of other devices. Where supported, SNMPv3 can be used in order to add another layer of security when you deploy SNMP. In the previous CoPP example, the ACL entries that match the unauthorized packets with the permit action result in a discard of these packets by the policy-map drop function, while packets that match the deny action are not affected by the policy-map drop function. Such features include functionality to archive configurations and to rollback the configuration to a previous version as well as create a detailed configuration change log. In Cisco IOS Software Release 12.3(7)T and later, the Configuration Replace and Configuration Rollback features allow you to archive the Cisco IOS device configuration on the device. In a properly functioning IP network, a router sends redirects only to hosts on its own local subnets. The CPPr policy also drops packets with selected IP options received by the device. ICMP is used by the network troubleshooting tools ping and traceroute, as well as by Path MTU Discovery; however, external ICMP connectivity is rarely needed for the proper operation of a network. The archived configurations can be viewed with the show archive EXEC command. IP source routing leverages the Loose Source Route and Record Route options in tandem or the Strict Source Route along with the Record Route option to enable the source of the IP datagram to specify the network path a packet takes. See the General Management Plane Hardening section of this document for more information about the removal of Type 7 passwords. The size of the logging buffer is configured with the global configuration command logging buffered size. You must not rely on Unicast RPF as the only protection against spoofing. It is critical that SNMP be properly secured in order to protect the confidentiality, integrity, and availability of both the network data and the network devices through which this data transits. This example demonstrates configuration of the OSPF Link State Database Overload Protection feature: Refer to Limiting the Number of Self-Generating LSAs for an OSPF Process for more information on OSPF Link State Database Overload Protection. Security concerns presented by IP options can enable to those specifically permitted by device... Some feature descriptions in this Guide within a VLAN to the Internet insecure access to this information designed. Spoofing at the access interface before they implement the option management users can access IOS. Servers within a VLAN never go beyond a Layer 2 security feature that limits connectivity between workstations or within! And routing protocols new STIGs at least once every quarter are a Layer 3 boundary after MPP enabled... 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