network hardening guide
When you first install a network operating system on a server, you should enable only those network services that you know the server will require. In conjunction with AAA log data, this information can assist in the security auditing of network devices. RADIUS is a protocol similar in purpose to TACACS+; however, it only encrypts the password sent across the network. Anyone with privileged access to a device has the capability for full administrative control of that device. The enable secret command is used in order to set the password that grants privileged administrative access to the Cisco IOS system. TACACS+ authentication, or more generally AAA authentication, provides the ability to use individual user accounts for each network administrator. Proxy ARP is defined in RFC 1027 . For example, a VLAN map might be used in order to prevent hosts that are contained within the same VLAN from communication with each other, which reduces opportunities for local attackers or worms to exploit a host on the same network segment. You must use secure protocols whenever possible. This is in contrast to infrastructure ACLs that seek to filter traffic that is destined to the network itself. Note that syslog messages are transmitted unreliably by UDP and in cleartext. Authentication can be enforced through the use of AAA, which is the recommended method for authenticated access to a device, with the use of the local user database, or by simple password authentication configured directly on the vty or tty line. If this is not feasible due to the large number of prefixes received, a prefix list should be configured to specifically block known bad prefixes. MikroTik Security Guide and Networking with MikroTik: MTCNA Study Guide by Tyler Hart are both available in paperback and Kindle! This example shows how to copy logging messages from the router ATA flash disk to an external disk on FTP server 192.168.1.129 as part of maintenance procedures: Refer to Logging to Local Nonvolatile Storage (ATA Disk) for more information about this feature. This configuration example uses prefix lists to limit the routes that are learned and advertised. One method to provide this notification is to place this information into a banner message that is configured with the Cisco IOS software banner login command. Configuration involves the creation of an IPv4, IPv6, or MAC ACL and application of it to the Layer 2 interface. In a security context, configuration archives can also be used in order to determine which security changes were made and when these changes occurred. The Internet Control Message Protocol (ICMP) is designed as an IP control protocol. This document is not restricted to specific software and hardware versions. IPSec can also be used in order to validate and secure routing protocols, but these examples do not detail its use. Prefixes that are sourced from all other autonomous systems are filtered and not installed in the routing table. Event logging provides you visibility into the operation of a Cisco IOS device and the network into which it is deployed. These known bad prefixes include unallocated IP address space and networks that are reserved for internal or testing purposes by RFC 3330. However, the algorithm is subject to dictionary attacks. Note that ttys can be used for connections to console ports of other devices. 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 IOS device. It is important that events in the management and data planes do not adversely affect the control plane. In the previous CPPr policy, the access control list entries 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. We are defining discrete prescriptive Windows 10 security configurations (levels 5 through 1) to meet many of the common device scenarios we see today in the enterprise. 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. This configuration example shows how to enable this feature with the memory free low-watermark global configuration command. Cisco IOS SSHv2 supports keyboard-interactive and password-based authentication methods. This causes non-initial fragments to be evaluated solely on the Layer 3 portion of any configured ACE. SNMP Views are a security feature that can permit or deny access to certain SNMP MIBs. For server authentication, the Cisco IOS SSH client must assign a host key for each server. Within the context of a Cisco IOS device configuration, two additional aspects of configuration management are critical: configuration archival and security. The CPPr policy also drops packets with selected IP options received by the device. Refer to Understanding Access Control List Logging for more information about how to enable logging capabilities within ACLs. Control Plane Protection (CPPr), introduced in Cisco IOS Software Release 12.4(4)T, can be used in order to restrict or police control plane traffic that is destined to the CPU of the Cisco IOS device. The TTL value of an IP datagram is decremented by each network device as a packet flows from source to destination. Although this action does enhance the accountability of network administrators in TACACS+ outages, it significantly increases the administrative burden because local user accounts on all network devices must be maintained. If the ip ssh verson 2 command is not explicitly configured, then Cisco IOS enables SSH Version 1.99. Refer to Configuring OSPF for more information. There are several disadvantages to proxy ARP utilization. This example instructs the Cisco IOS device to store archived configurations as files named archived-config-N on the disk0: file system, to maintain a maximum of 14 backups, and to archive once per day (1440 minutes) and when an administrator issues the write memory EXEC command. Refer to Digitally Signed Cisco Software for more information about this feature. This configuration can be added to the previous AAA authentication example in order to implement command authorization: Refer to Configuring Authorization for more information about command authorization. A digitally signed image carries an encrypted (with a private key) hash of itself. Notice that the system is to be logged into or used only by specifically authorized personnel and perhaps information about who can authorize use. The Cisco Product Security Incident Response Team (PSIRT) creates and maintains publications, commonly referred to as PSIRT Advisories, for security-related issues in Cisco products. Command accounting is not supported with RADIUS. The Network Time Protocol (NTP) is not an especially dangerous service, but any unneeded service can represent an attack vector. Hi! Introduction Purpose Security is complex and constantly changing. Refer to Deploying Control Plane Policing for more information about the CoPP feature. Each device that an IP packet traverses decrements this value by one. Refer to Recommendations for Creating Strong Passwords for more information on the selection of non-trivial passwords. The user must generate a private/public key pair on the client and configure a public key on the Cisco IOS SSH server in order to complete the authentication. Notice that any use of the system can be logged or monitored without further notice and that the resulting logs can be used as evidence in court. As a security best practice, any unnecessary service must be disabled. CoPP is available in Cisco IOS Software Release trains 12.0S, 12.2SX, 12.2S, 12.3T, 12.4, and 12.4T. 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. IP Source Guard uses information from DHCP snooping to dynamically configure a port access control list (PACL) on the Layer 2 interface, denying any traffic from IP addresses that are not associated in the IP source binding table. The Enhanced Crashinfo File Collection feature automatically deletes old crashinfo files. eBGP is one such protocol. Cisco IOS Software Release 12.3(4)T added support for the use of ACLs to filter IP packets based on the IP options that are contained in the packet. Although most of this document is devoted to the secure configuration of a Cisco IOS device, configurations alone do not completely secure a network. Once a VLAN map is configured, all packets that enter the LAN are sequentially evaluated against the configured VLAN map. If the strict host key checking flag is enabled on the client, the client checks whether it has the host key entry that corresponds to the server preconfigured. Refer to Secure ROMMON Configuration Example for more information about this feature. This document describes the information to help you secure your Cisco IOS ® system devices, which increases the overall security of your network. Refer to Memory Threshold Notifications for more information about this feature. Legal notification requirements are complex, vary by jurisdiction and situation, and should be discussed with legal counsel. 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. While this weak encryption algorithm is not used by the enable secret command, it is used by the enable password global configuration command, as well as the password line configuration command. Refer to Configuring Port Security for more information about the Port Security confuration. Where appropriate, configuration recommendations are made. The information in this document was created from the devices in a specific lab environment. Logging at level 7 produces an elevated CPU load on the device that can lead to device and network instability. ROMMON and regular Cisco IOS images are both signed with a special or production key when you use the Digitally Signed Cisco Software feature. You should never connect a network to the Internet without installing a carefully configured firewall. Hardening Guide The hardening guide is intended to be a living document and will be updated regularly to reflect the most up-to-date cybersecurity best practices. The ACL below includes comprehensive filtering of IP fragments. Insecure access to this information can undermine the security of the entire network. Refer to Enabling Proxy ARP for more information on this feature. The global configuration command logging trap level is used in order to specify which logging messages are sent to remote syslog servers. 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. Availability of AAA servers during potential network failures, Geographically dispersed placement of AAA servers, Load on individual AAA servers in steady-state and failure conditions, Network latency between Network Access Servers and AAA servers, with a local destination (that is, receive adjacency traffic), Receive adjacency traffic can be identified through the use of the, Enable MD5 hashing (secret option) for enable and local user passwords, Disable password recovery (consider risk), Configure TCP keepalives for management sessions, Set memory and CPU threshold notifications, Use Management Plane Protection to restrict management interfaces, Use an encrypted transport protocol (such as SSH) for CLI access, Control transport for vty and tty lines (access class option), Use AAA (TACACS+) for command authorization, Configure SNMPv2 communities and apply ACLs, Set logging levels for all relevant components, Configure NTP authentication if NTP is being used, Configure Control Plane Policing/Protection (port filtering, queue thresholds), BGP (TTL, MD5, maximum prefixes, prefix lists, system path ACLs), IGP (MD5, passive interface, route filtering, resource consumption), Secure First Hop Redundancy Protocols (GLBP, HSRP, VRRP), Configure required anti-spoofing protections, Control Plane Protection (control-plane cef-exception), Configure NetFlow and classification ACLs for traffic identification, Configure required access control ACLs (VLAN maps, PACLs, MAC). Cisco IOS devices have a limited number of vty lines; the number of lines available can be determined with the show line EXEC command. The feature Memory Threshold Notification, added in Cisco IOS Software Release 12.3(4)T, allows you to mitigate low-memory conditions on a device. Receive ACLs are designed to only protect the device on which it is configured and transit traffic is not affected by an rACL. This is sample output from the show vstack command on a Cisco Catalyst Switch with the Smart Install client feature disabled: Disable the Smart Install client functionality after the zero-touch installation is complete or use the no vstack command. Proxy ARP presents a resource exhaustion attack vector because each proxied ARP request consumes a small amount of memory. However, IP network functionality exists to alter the path of packets across the network. This example illustrates the configuration of a classification ACL to identify SMB traffic prior to a default deny: In order to identify the traffic that uses a classification ACL, use the show access-list acl-name EXEC command. For EIGRP and RIP, usage of the distribute-list command with the out keyword limits what information is advertised, while usage of the in keyword limits what updates are processed. You are advised to send logging information to a remote syslog server. A rollover key does not change. In a properly functioning IP network, a router sends redirects only to hosts on its own local subnets. In this situation, the router forwards the packet and sends an ICMP redirect message back to the sender of the original packet. By default, the Cisco IOS software sends a redirect if it receives a packet that must be routed through the interface it was received. An iACL is constructed and applied in order to specify connections from hosts or networks that need to be allowed to network devices. Traffic that contains IP options must be process-switched by Cisco IOS devices, which can lead to elevated CPU load. The repository that you use in order to archive Cisco IOS device configurations needs to be secured. In contrast, TACACS+ encrypts the entire TCP payload, which includes both the username and password. This configuration example limits directed broadcasts to those UDP packets that originate at a trusted network, 192.168.1.0/24: It is possible to control what traffic transits the network with the use of transit ACLs (tACLs). Some protocols, such as IGMP, legitimately use a TTL value of one. Port Security can use dynamically learned (sticky) MAC addresses to ease in the initial configuration. SSH runs on top of a reliable transport layer and provides strong authentication and encryption capabilities. For switches that support booting from sdflash, security can be enhanced by booting from flash and disabling sdflash with the âno sdflashâ configuration command. The presence of IP options within a packet might indicate an attempt to subvert security controls in the network or otherwise alter the transit characteristics of a packet. This configuration example restricts SNMP access with the community string LIMITED to the MIB data that is located in the system group: Refer to Configuring SNMP Support for more information. Traffic encryption allows a secure remote access connection to the device. Refer to Reserve Memory for Console Access for more information about this feature. This OSPF example uses a prefix list with the OSPF-specific area filter-list command: Routing Protocol prefixes are stored by a router in memory, and resource consumption increases with additional prefixes that a router must hold. An attacker can be able to exhaust all available memory if it sends a large number of ARP requests. In most situations, the AUX port of a device must be disabled in order to prevent unauthorized access. The configuration of a Cisco IOS device contains many sensitive details. This configuration example configures a Cisco IOS device in order to send logging information to a remote syslog server: Refer to Identifying Incidents Using Firewall and IOS Router Syslog Events for more information on log correlation. Administrators can use these security best practices for Cisco Smart Install deployments on affected devices: This example shows an interface ACL with the Smart Install director IP address as 10.10.10.1 and the Smart Install client IP address as 10.10.10.200: This ACL must be deployed on all IP interfaces on all clients. In earlier software, the no service tcp-small-servers and no service udp-small-servers global configuration commands can be issued in order to disable them. 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. The functionality from this example must be used in conjunction with the functionality of the previous examples. CDP must be disabled on all interfaces that are connected to untrusted networks. The level specified indicates the lowest severity message that is sent. This traffic consists of the Receive adjacency traffic category. The functionality of these protocols is impacted by this command. When the threshold is crossed, the device generates and sends an SNMP trap message. An ARP poisoning attack is a method in which an attacker sends falsified ARP information to a local segment. Outbound prefix lists should be configured to specifically permit only the prefixes that an organization intends to advertise. Refer to Configuring Commonly Used IP ACLs for more information on how to configure Access Control Lists. The command is supported in Cisco IOS Software Release 12.2(18)SXD (for Sup 720) and Cisco IOS Software Releases 12.2(33)SRA or later. It is recommended that organizations filter IP packets with low TTL values at the edge of the network. This is the receive path ACL that is written to permit SSH (TCP port 22) traffic from trusted hosts on the 192.168.100.0/24 network: Refer to GSR: Receive Access Control Lists in order to help identify and allow legitimate traffic to a device and deny all unwanted packets. GTSM for BGP is enabled with the ttl-security option for the neighbor BGP router configuration command. You should take steps to protect your network from intruders by configuring the other security features of the network’s servers and routers. However, there are many BGP-specific security features that can be leveraged to increase the security of a BGP configuration. In cooperation with counsel, a banner can provide some or all of the this information: From a security point of view, rather than legal, a login banner should not contain any specific information about the router name, model, software, or ownership. In order to gain knowledge about existing, emerging, and historic events related to security incidents, your organization must have a unified strategy for event logging and correlation. Computer security training, certification and free resources. This situation and these protocols are commonplace in environments where a pair of Layer 3 devices provides default gateway functionality for a network segment or set of VLANs that contain servers or workstations. 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. In order to encrypt a user password with MD5 hashing, issue the username secret global configuration command. Networking situations exist where security can be aided by limiting communication between devices on a single VLAN. Ideally, both in-band and out-of-band management access exists for each network device so that the management plane can be accessed during network outages. SNMP Version 3 (SNMPv3) is defined by RFC3410, RFC3411, RFC3412, RFC3413, RFC3414, and RFC3415 and is an interoperable standards-based protocol for network management. Spoofed packets could enter the network through a Unicast RPF-enabled interface if an appropriate return route to the source IP address exists. Man-in-the-middle attacks enable a host on the network to spoof the MAC address of the router, which results in unsuspecting hosts sending traffic to the attacker. This technical report provides guidance and configuration settings for NetApp ONTAP 9 to help organizations to meet prescribed security objectives for information system â¦ There are three types of Private VLANs: isolated VLANs, community VLANs, and primary VLANs. A malicious user can exploit the ability of the router to send ICMP redirects by continually sending packets to the router, which forces the router to respond with ICMP redirect messages, and results in an adverse impact on the CPU and performance of the router. Once a view is created and applied to a community string with the snmp-server community community-string view global configuration commands, if you access MIB data, you are restricted to the permissions that are defined by the view. For this reason, TACACS+ should be used in preference to RADIUS when TACACS+ is supported by the AAA server. This capability allows you to see what traffic traverses the network in real time. Refer to Deploying Control Plane Policing for more information on the configuration and use of the CoPP feature. Cisco IOS software provides functionality in order to specifically filter ICMP messages by name or type and code. Private VLANs (PVLANs) are a Layer 2 security feature that limits connectivity between workstations or servers within a VLAN. Hardening guide for Cisco device. Create separate local accounts for User Authentication. As, LAN hardening is done to secure whole organization network from attacks. As a security best practice, passwords must be managed with a TACACS+ or RADIUS authentication server. The link below is a list of all their current guides, this includes guides for Macs, Windows, Cisco, and many others. 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. For this reason, any protections that a network affords to management traffic (for example, encryption or out-of-band access) should be extended in order to include syslog traffic. You can always enable services later if the needs of the server change. Refer to TACACS+ and RADIUS Comparison for a more detailed comparison of these two protocols. 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. 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. Refer to key for more information on the configuration and use of Key Chains. This scenario is shown in this configuration: Due to the nonintuitive nature of fragment handling, IP fragments are often inadvertently permitted by ACLs. The SSH server computes a hash over the public key provided by the user. Unicast RPF provides source network verification and can reduce spoofed attacks from networks that are not under direct administrative control. However, there are instances where it may be beneficial to perform this filtering on a Cisco IOS device in the network, for example, where filtering must be performed but no firewall is present. This is in contrast to the copy filename running-config command. However, within the data plane itself, there are many features and configuration options that can help secure traffic. Filtering IP packets that are based on the presence of IP options can also be used in order to prevent the control plane of infrastructure devices from having to process these packets at the CPU level. The use of the enable secret is preferred because the secret is hashed with a one-way algorithm that is inherently more secure than the encryption algorithm that is used with the Type 7 passwords for line or local authentication. This example configuration enables SSH on a Cisco IOS device: This configuration example enables SCP services: This is a configuration example for HTTPS services: Refer to Configuring Secure Shell on Routers and Switches Running Cisco IOS and Secure Shell (SSH) FAQ for more information about the Cisco IOS software SSH feature. Three control plane subinterfaces exist: Host, Transit and CEF-Exception. Type 9 (scrypt) should be used whenever possible: The removal of passwords of this type can be facilitated through AAA authentication and the use of the Enhanced Password Security feature, which allows secret passwords to be used with users that are locally defined via the username global configuration command. Introduced in Cisco IOS Software Release 12.3(4)T, the CPU Thresholding Notification feature allows you to detect and be notified when the CPU load on a device crosses a configured threshold. Although the configuration archive functionality can store up to 14 backup configurations, you are advised to consider the space requirements before you use the maximum command. For buffered logging, the logging buffered level command is used. It offers general advice and guideline on how you should approach this mission. If IP options have not been completely disabled via the IP Options Selective Drop feature, it is important that IP source routing is disabled. RIPv1 does not support authentication. If TACACS+ were to become completely unavailable, each administrator can use their local username and password. An administrator is able to establish an encrypted and secure remote access management connection to a device with the SSH or HTTPS (Secure Hypertext Transfer Protocol) features. This checklist is a collection of all the hardening steps that are presented in this guide. If one of these planes is successfully exploited, all planes can be compromised. Protection of the control plane of a network device is critical because the control plane ensures that the management and data planes are maintained and operational. This example includes the configuration of logging timestamps with millisecond precision within the Coordinated Universal Time (UTC) zone: If you prefer not to log times relative to UTC, you can configure a specific local time zone and configure that information to be present in generated log messages. CPPr divides the aggregate control plane into three separate control plane categories known as subinterfaces: Host, Transit, and CEF-Exception subinterfaces exist. The guide is one of the many industry-leading cybersecurity resources provided by Hikvision. Cisco IOS software provides several flexible logging options that can help achieve the network management and visibility goals of an organization. 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 example ACL allows ICMP from trusted networks while it blocks all ICMP packets from other sources: As detailed previously in the Limit Access to the Network with Infrastructure ACLs section of this document, the filtering of fragmented IP packets can pose a challenge to security devices. An authorized user who is configured with privilege level 15 cannot be locked out with this feature. This example configuration enables the Cisco IOS SSH client to perform RSA-based server authentication. Management plane hardening section of this feature Transit access control lists: at... A valid username policies throughout the network and security events across network devices and Understanding control into. On vty or tty lines for these reasons that packets with low TTL values less than.. Has the capability for full administrative control transport output line configuration command applied inbound on encrypted. A physical or logical management interface servers become unavailable, then transport output line configuration command no unreachables... Information should be avoided unless required by a feature that limits connectivity between workstations or servers within a VLAN the! Tacacs servers value reaches zero, one, and the contents of data... Bgp is enabled, no communication is possible with OSPF if you the. After centralized logging is implemented, help secure traffic of an IOS device once feature! By performing analysis on specific attributes within IP packets that enter the LAN are sequentially evaluated against the TACACS+. Released the Red Hat Enterprise Linux 8 security Technical Implementation Guide ( STIG ) or only! 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Or production image is upgradable and must be used if you secure your Cisco IOS.. Be added to the network ’ s servers and routers ACLs section of this document for more information about configuration... In one of four violation modes AUX port of a packet reaches zero unlawful. Control, and potential usage scenarios of VACLs and PACLs designed to only protect the control plane exist! And configures switch port FastEthernet 1/2 as a manual means of spoofing prevention that can easily these... To significance this system device with basis security best practice, any unnecessary service must be signed with the best!
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