Protecting in layers means to protect at the host level, the application level, the operating system level, the user level, the physical level and all the sublevels in between. The syntax for PACLs creation, which takes precedence over VLAN maps and router ACLs, is the same as router ACLs. In the next few lessons, we'll do a deep dive on the best practices that an IT support specialist should know for implementing network hardening. If you cannot fully prevent the use of Type 7 passwords, consider these passwords obfuscated, not encrypted. The Authentication, Authorization, and Accounting (AAA) framework is vital to secure network devices. GTSM for BGP is enabled with the ttl-security option for the neighbor BGP router configuration command. NetFlow enables you to monitor traffic flows in the network. If no enable secret is set and a password is configured for the console tty line, the console password can be used in order to receive privileged access, even from a remote virtual tty (vty) session. The signature and the user's public key are sent to the SSH server for authentication. This section highlights several methods that can be used in order to secure the deployment of SNMP within IOS devices. For this reason, it is recommended that the transmission of ICMP redirects be disabled. A rollover key does not change. Sample configuration using NTP authentication: Security best practices around the Cisco Smart Install (SMI) feature depend on how the feature is used in a specific customer environment. BGP is often targeted by attackers because of its ubiquity and the set and forget nature of BGP configurations in smaller organizations. 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. Cisco IOS software provides a password recovery procedure that relies upon access to ROM Monitor Mode (ROMMON) using the Break key during system startup. The National Security Agency publishes some amazing hardening guides, and security information. This interface command has to be applied on the ingress interface and it instructs the forwarding engine to not inspect the IP header. 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. This feature also allows configuration of the number of crashinfo files to be saved. Port Security can be used in order to validate MAC addresses at the access layer. System hardening is needed throughout the lifecycle of technology, from initial installation, through configuration, maintenance, and support, to end-of-life decommissioning. If no service password-recovery is enabled on a device, it is recommended that an offline copy of the device configuration be saved and that a configuration archiving solution be implemented. Port Security is used in order to mitigate MAC address spoofing at the access interface. These global configuration commands can be used in order to enable this feature. In order to prevent resource exhaustion, it is important to configure the routing protocol to limit resource consumption. Management sessions to devices allow you the ability to view and collect information about a device and its operations. Upon check, the device decrypts the hash with the corresponding public key from the keys it has in its key store and also calculates its own hash of the image. This section provides information about physically securing domain controllers, whether the domain controllers are physical or virtual machines, in datacenter locations, branch offices, and even remote locations with only basic infrastructure controls. 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. After centralized logging is implemented, you must develop a structured approach to log analysis and incident tracking. 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. All of the devices used in this document started with a cleared (default) configuration. During configuration of the ip verify interface configuration command, the keyword any configures loose mode while the keyword rx configures strict mode. Firewall Configuration. This function allows a device with tty lines to act as a console server where connections can be established across the network to the console ports of devices connected to the tty lines. This traffic contains an entry in the Cisco Express Forwarding (CEF) table whereby the next router hop is the device itself, which is indicated by the term receive in the show ip cef CLI output. Command accounting is not supported with RADIUS. The rACL protects the device from harmful traffic before the traffic impacts the route processor. DISA releases new STIGs at least once every quarter. This example ACL filters packets with TTL values less than six. Added to Cisco IOS Software Release 12.3(14)T, the Exclusive Configuration Change Access feature ensures that only one administrator makes configuration changes to a Cisco IOS device at a given time. 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. 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. However, there are many BGP-specific security features that can be leveraged to increase the security of a BGP configuration. The Ubiquiti EdgeRouter Hardening Guide is over 30 pages of router security commands, advice, and best practices that you can implement in your networks. The functionality of these protocols is impacted by this command. The created digest is then stored in TCP option Kind 19, which was created specifically for this purpose by RFC 2385 . The coverage of security features in this document often provides enough detail for you to configure the feature. Infrastructure access control lists (iACLs). The AAA server then uses its configured policies in order to permit or deny the command for that particular user. NetFlow flows can be created with sampled traffic data in high-volume environments. The hash is used in order to determine if the server has an entry that matches. The CoPP feature can also be used in order to restrict IP packets that are destined to the infrastructure device. By adding MD5 hash capabilities to the authentication process, routing updates no longer contain cleartext passwords, and the entire contents of the routing update is more resistant to tampering. 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. However, within the data plane itself, there are many features and configuration options that can help secure traffic. By using password authentication with routing protocols between routers, you can aid the security of the network. You can always enable services later if the needs of the server change. The protections provided by iACLs are relevant to both the management and control planes. MAC access control lists or extended lists can be applied on IP network with the use of this command in interface configuration mode: Note: It is to classify Layer 3 packets as Layer 2 packets. Hackers regularly find security holes in network operating systems. The Border Gateway Protocol (BGP) is the routing foundation of the Internet. Digitally signed Cisco software keys are identified by the type and version of the key. If SSH is enabled, it is recommended to disable SSHv1 by using the ip ssh version 2 command. Note: CPPr does not support IPv6 and is restricted to the IPv4 input path. If NTP is used, it is important to explicitly configure a trusted time source and to use proper authentication. It is recommended that organizations filter IP packets with low TTL values at the edge of the network. Hardening refers to providing various means of protection in a computer system. In Cisco IOS Software Release 12.3(4)T and later, Cisco IOS software supports the use of ACLs to filter IP packets based on the IP options that are contained in the packet. Customers who leverage the Smart Install feature for more than zero-touch deployment (configuration and image management). Customers who do not use the Smart Install feature. In order to prevent this type of attack, all FHRPs that are supported by Cisco IOS software include an authentication capability with either MD5 or text strings. This allows the administrator to apply policies throughout the network for the management plane. In contrast, TACACS+ encrypts the entire TCP payload, which includes both the username and password. This configuration example illustrates the use of the logging source-interface interface global configuration command in order to specify that the IP address of the loopback 0 interface be used for all log messages: Refer to the Cisco IOS Command Reference for more information. If IP options have not been completely disabled via the IP Options Selective Drop feature, it is important that IP source routing is disabled. The ACEs that make up this ACL are not comprehensive. Hi! 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. In addition to the community string, an ACL should be applied that further restricts SNMP access to a select group of source IP addresses. 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. BGP autonomous system (AS) path access lists allows the user to filter received and advertised prefixes based on the AS-path attribute of a prefix. By "faking" its identity, the router accepts responsibility for routing packets to the real destination. The example below also configures interface FastEthernet 1/1 as an isolated port in VLAN 11: A secondary VLAN that is configured as a community VLAN allows communication among members of the VLAN as well as with any promiscuous ports in the primary VLAN. This presents a DoS attack vector. 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. Mikrotik routers straight out of the box require security hardening like any Arista, Cisco, Juniper, or Ubiquiti router. ROMMON and regular Cisco IOS images are both signed with a special or production key when you use the Digitally Signed Cisco Software feature. Completely filtering packets with TTL values insufficient to traverse the network mitigates the threat of TTL-based attacks. 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. The Internet Control Message Protocol (ICMP) was designed as a control protocol for IP. Implement one hardening aspect at a time and then test all server and application functionality. Subsequent methods are only attempted in cases where earlier methods fail due to server unavailability or incorrect configuration. You should take steps to protect your network from intruders by configuring the other security features of the network’s servers and routers. Cisco IOS software uses the first listed method that successfully accepts or rejects a user. In order to prevent the router from sending ICMP redirects, use the no ip redirects interface configuration command. Unless specifically required, you are advised to avoid logging at level 7. An administrator might also separate the implicit deny at the end of an ACL into granular ACEs to help identify the types of denied traffic. Examples of packets that are classified for the host subinterface category include management traffic such as SSH or Telnet and routing protocols. This requires a level of CPU effort that is not required for typical packets that traverse the network. An authorized user who is configured with privilege level 15 cannot be locked out with this feature. Often an attacker uses ARP poisoning in order to perform a man-in-the-middle attack. 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. Spoofed packets could enter the network through a Unicast RPF-enabled interface if an appropriate return route to the source IP address exists. Typical configurations include the use of local or enable authentication if all configured TACACS+ servers are unavailable. This example illustrates the configuration of this feature for automatic configuration locking: Added in Cisco IOS Software Release 12.3(8)T, the Resilient Configuration feature makes it possible to securely store a copy of the Cisco IOS software image and device configuration that is currently used by a Cisco IOS device. The community VLAN, VLAN 12, is a secondary VLAN to primary VLAN 20. Proxy ARP presents a resource exhaustion attack vector because each proxied ARP request consumes a small amount of memory. This information can be abused by malicious users. However, SSH must still be enforced as the transport even when IPSec is used. 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. Customers who leverage the Smart Install feature only for zero-touch deployment. It is important that events in the management and data planes do not adversely affect the control plane. If the decrypted hash matches the calculated image hash, the image has not been tampered with and can be trusted. Infrastructure ACLs (iACLs) can be deployed in order to ensure that only end hosts with trusted IP addresses can send SNMP traffic to an IOS device. In an effort to prevent information disclosure or unauthorized access to the data that is transmitted between the administrator and the device, transport input ssh should be used instead of clear-text protocols, such as Telnet and rlogin. These sections provide an overview of the features, benefits, and potential usage scenarios of VACLs and PACLs. 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. Create separate local accounts for User Authentication. 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