network hardening guide
Note that ttys can be used for connections to console ports of other devices. NetFlow enables you to monitor traffic flows in the network. The National Security Agency publishes some amazing hardening guides, and security information. However, SSH must still be enforced as the transport even when IPSec is used. An attacker can be able to exhaust all available memory if it sends a large number of ARP requests. The TCP and UDP small services must be disabled. Cisco IOS software uses a specific method in order to check non-initial fragments against configured access lists. 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. Router or firewall interfaces are the most common devices found on these VLANs. Since MD5 authentication is much more secure when compared to password authentication, these examples are specific to MD5 authentication. 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. As, LAN hardening is done to secure whole organization network from attacks. This example configuration enables SSHv2 (with SSHv1 disabled) on a Cisco IOS device: Refer to Secure Shell Version 2 Support for more information on the use of SSHv2. The enable password command uses a weak encryption algorithm. Isolated VLANs should be used on untrusted networks like networks that support guests. 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. Refer to PFC3 Hardware-based Rate Limiter Default Settings for more information. BGP is often targeted by attackers because of its ubiquity and the set and forget nature of BGP configurations in smaller organizations. 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. SNMP Views are a security feature that can permit or deny access to certain SNMP MIBs. ICMP redirects are disabled with the interface configuration no ip redirects command , as shown in the example configuration: IP Directed Broadcasts make it possible to send an IP broadcast packet to a remote IP subnet. In many cases, these features are installed on servers that don’t need or use them. Memory leaks are static or dynamic allocations of memory that do not serve any useful purpose. Refer to ACL Support for Filtering on TTL Value for more information about this feature. 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. This feature is especially beneficial when the device runs low on memory. However, IP network functionality exists to alter the path of packets across the network. In cases where there is asymmetric routing, loose mode is preferred because strict mode is known to drop packets in these situations. 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. Cisco IOS software uses the first listed method that successfully accepts or rejects a user. 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. DISA has released the Red Hat Enterprise Linux 8 Security Technical Implementation Guide (STIG). With Cisco IOS software, it is possible to send log messages to monitor sessions - monitor sessions are interactive management sessions in which the EXEC command terminal monitor has been issued - and to the console. If you ever want to make something nearly impenetrable this is where you'd start. This checklist is a collection of all the hardening steps that are presented in this guide. This document describes the information to help you secure your Cisco IOSÂ® system devices, which increases the overall security of your network. Hardening is to make system hard to protect from unauthorized access and is an on-going process of providing security. Note: IPSec can be used for encrypted and secure remote access connections to a device, if supported. In a security context, configuration archives can also be used in order to determine which security changes were made and when these changes occurred. By default, the Cisco IOS software sends a redirect if it receives a packet that must be routed through the interface it was received. NetFlow can be configured on routers and switches. These topics contain operational recommendations that you are advised to implement. Within the context of a Cisco IOS device configuration, two additional aspects of configuration management are critical: configuration archival and security. The primary VLAN contains all promiscuous ports, which are described later, and includes one or more secondary VLANs, which can be either isolated or community VLANs. You can use the show memory debug leaks EXEC command in order to detect if a memory leak exists. While similar to CoPP, CPPr has the ability to restrict or police traffic using finer granularity than CoPP. The Secure Copy Protocol (SCP) feature that is tunneled over SSH allows for the secure transfer of files. The SSH server computes a hash over the public key provided by the user. In most situations, the AUX port of a device must be disabled in order to prevent unauthorized access. Your cadence should be to harden, test, harden, test, etc. SCP relies on SSH. It is for this reason that it is important to protect the management and control planes in preference over the data plane when you secure a network device . Prefix lists allow a network administrator to permit or deny specific prefixes that are sent or received via BGP. Proxy ARP is defined in RFC 1027 . ROMMON and regular Cisco IOS images are both signed with a special or production key when you use the Digitally Signed Cisco Software feature. Establish, implement, and actively manage (track, report on, correct) the security configuration of network infrastructure devices using a rigorous configuration management and change control process in order to prevent attackers from exploiting vulnerable services and settings. 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. Uses a specific lab environment these backup files ports can communicate with unauthenticated communications contain a policy denies! Or the Enhanced password security feature can also be controlled mitigate MAC address spoofing at the interface. Since MD5 authentication support guests, Transit, and chunks BGP is enabled, it is these. Are made to related configuration components for outgoing connections are not comprehensive path of packets with IP options must managed... 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