Recommendations and examples that cover Routing Information Protocol Version 2 (RIPv2), Enhanced Interior Gateway Routing Protocol (EIGRP), and Open Shortest Path First (OSPF) are provided when appropriate. Refer to ACL Support for Filtering on TTL Value for more information about this functionality. 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. For production environments, community strings should be chosen with caution and should consist of a series of alphabetical, numerical, and non-alphanumeric symbols. It also does not allow malicious users to change the configuration register value and access NVRAM. These sections detail these features and options such that you can more easily secure your network. There are several disadvantages to proxy ARP utilization. Dynamic Address Resolution Protocol (ARP) Inspection (DAI) mitigates attack vectors that use ARP poisoning on local segments. The second type of traffic that is handled by the CPU is data plane traffic - traffic with a destination beyond the Cisco IOS device itself - which requires special processing by the CPU. This provides protection against TTL expiry attacks for networks up to five hops in width. In DHCP environments, DAI uses the data that is generated by the DHCP snooping feature. In a dictionary attack, an attacker tries every word in a dictionary or other list of candidate passwords in order to find a match. This is an example configuration for OSPF router authentication using MD5. Any Cisco IOS configuration file that contains encrypted passwords must be treated with the same care that is used for a cleartext list of those same passwords. The MPP feature allows an administrator to designate one or more interfaces as management interfaces. 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. 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. All transit traffic that crosses the network and is not destined to infrastructure devices is then explicitly permitted. Even within jurisdictions, legal opinions can differ. Router or firewall interfaces are the most common devices found on these VLANs. Configured prefix lists limit the prefixes that are sent or received to those specifically permitted by the routing policy of a network. Often an attacker uses ARP poisoning in order to perform a man-in-the-middle attack. Without PVLANs, all devices on a Layer 2 VLAN can communicate freely. 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. Protocols that leverage virtual MAC addresses such as HSRP do not function when the maximum number is set to one. You are advised not to advertise any information to networks that are outside your administrative control. Cisco IOS software evaluates these non-initial fragments against the ACL and ignores any Layer 4 filtering information. There are no specific requirements for this document. This provides an overview of the most important BGP security features. It is for these reasons that IP fragments are often used in attacks and should be explicitly filtered at the top of any configured tACLs. SSHv1 is considered to be insecure and can have adverse effects on the system. Subinterfaces exist for Host, Transit, and CEF-Exception traffic categories. The small services are disabled by default in Cisco IOS Software Releases 12.0 and later. A digitally signed image carries an encrypted (with a private key) hash of itself. The device that decrements the TTL to zero, and therefore drops the packet, is required in order to generate and send an ICMP Time Exceeded message to the source of the packet. Information leaks, or the introduction of false information into an IGP, can be mitigated through use of the passive-interface command that assists in controlling the advertisement of routing information. DISA has released the Red Hat Enterprise Linux 8 Security Technical Implementation Guide (STIG). Routers can perform this function when the number of IP packets that are due to expire is low, but if the number of packets due to expire is high, generation and transmission of these messages can consume all available CPU resources. BGP is often targeted by attackers because of its ubiquity and the set and forget nature of BGP configurations in smaller organizations. The filtering provided by tACLs is beneficial when it is desirable to filter traffic to a particular group of devices or traffic that transits the network. Hi! These modes are protect, restrict, shutdown, and shutdown VLAN. 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. Cisco IOS software supports SSH Version 1.0 (SSHv1), SSH Version 2.0 (SSHv2), and HTTPS that uses Secure Sockets Layer (SSL) and Transport Layer Security (TLS) for authentication and data encryption. Traffic encryption allows a secure remote access connection to the device. In order to further restrict access to all the clients within the infrastructure, administrators can use these security best practices on other devices in the network: Devised to prevent unauthorized direct communication to network devices, infrastructure access control lists (iACLs) are one of the most critical security controls that can be implemented in networks. 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. 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. These sections provide a brief overview of each feature. When the threshold is crossed, the device generates and sends an SNMP trap message. In order to prevent the router from sending ICMP redirects, use the no ip redirects interface configuration command. Completely filtering packets with TTL values insufficient to traverse the network mitigates the threat of TTL-based attacks. 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. Harden your Windows Server 2019 servers or server templates incrementally. Split Network Services. In contrast, TACACS+ encrypts the entire TCP payload, which includes both the username and password. If your system has more than one network interface, bind MongoDB programs to the private or internal network interface. By default, IGPs are dynamic and discover additional routers that communicate with the particular IGP in use. This configuration example shows the use of these commands: Refer to Cisco IOS Network Management Command Reference for more information about global configuration commands. 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. Should a data plane event such as a DoS attack impact the control plane, the entire network can become unstable. Note: The devices that are permitted by these ACLs require the proper community string in order to access the requested SNMP information. You should take steps to protect your network from intruders by configuring the other security features of the network’s servers and routers. Refer to Reserve Memory for Console Access for more information about this feature. 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. Introduced in Cisco IOS Software Release 12.3(8)T1, the Memory Leak Detector feature allows you to detect memory leaks on a device. You can issue the memory reserve console global configuration command in order to enable this feature. Some feature descriptions in this document were written by Cisco information development teams. The starting value varies by operating system and typically ranges from 64 to 255. Introduction Purpose Security is complex and constantly changing. 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 the ip ssh verson 2 command is not explicitly configured, then Cisco IOS enables SSH Version 1.99. Download NNT's Guide to Hardening Ports, Protocols & Services. 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. 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. Proxy ARP presents a resource exhaustion attack vector because each proxied ARP request consumes a small amount of memory. Because application performance and end-user experience can suffer without the presence of data and management traffic, the survivability of the control plane ensures that the other two planes are maintained and operational. The Configuration Change Notification and Logging feature, added in Cisco IOS Software Release 12.3(4)T, makes it possible to log the configuration changes made to a Cisco IOS device. These known bad prefixes include unallocated IP address space and networks that are reserved for internal or testing purposes by RFC 3330. Isolated VLANs should be used on untrusted networks like networks that support guests. 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. The level specified indicates the lowest severity message that is sent. Because information can be disclosed in an interactive management session, this traffic must be encrypted so that a malicious user cannot gain access to the data that is transmitted. Promiscuous ports can communicate with all other ports in the primary and secondary VLANs. The lowest severity included in the buffer is configured with the logging buffered severity command. In order to deny packets from using a VLAN map, you can create an access control list (ACL) that matches the traffic and, in the VLAN map, set the action to drop. The Authentication, Authorization, and Accounting (AAA) framework is vital to secure network devices. Memory leaks are static or dynamic allocations of memory that do not serve any useful purpose. The NIST SP 800-123 Guide to General Server Security contains NIST recommendations on how to secure your servers. This example configuration enables the Cisco IOS SSH server to perform RSA-based user authentication. Once a VLAN map is configured, all packets that enter the LAN are sequentially evaluated against the configured VLAN map. 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. IP Source Guard is an effective means of spoofing prevention that can be used if you have control over Layer 2 interfaces. Control Plane Policing (CoPP). Refer to Configuring the Cisco IOS SSH Client to Perform RSA-Based Server Authentication for more information on the use of RSA keys with SSHv2. This helps ensure that interactive management access, such as SSH, is possible if an AAA server is unavailable. 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). Common hardening guidelines focus on systems as stand-alone elements, but the network environment also must be considered in building a secure system. IP options also include the functionality to alter the path that traffic takes through the network, which potentially allows it to subvert security controls. A device can also have other password information present within its configuration, such as an NTP key, SNMP community string, or Routing Protocol key. The engine ID can be displayed with the show snmp engineID command as shown in this example: Note: If the engineID is changed, all SNMP user accounts must be reconfigured. Settings for infrastructure such as Domain Name System servers, Simple Network Management Protocol configuration and time synchronization are a good starting point. The tty lines for these reverse connections over the network must also be controlled. When the client tries to establish an SSH session with a server, it receives the signature of the server as part of the key exchange message. SCP relies on SSH. A secure protocol choice includes the use of SSH instead of Telnet so that both authentication data and management information are encrypted. The Enhanced Password Security feature cannot be used with protocols that require the cleartext password to be retrievable, such as CHAP. Customers who do not use the Smart Install feature. In a security context, configuration archives can also be used in order to determine which security changes were made and when these changes occurred. 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. 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. Computer security training, certification and free resources. Mistakes to avoid. The syntax for PACLs creation, which takes precedence over VLAN maps and router ACLs, is the same as router ACLs. 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. As such, the messages it conveys can have far-reaching ramifications to the TCP and IP protocols in general. 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. Note: IPSec can be used for encrypted and secure remote access connections to a device, if supported. This standard was written to provide a minimum standard for the baseline of Window Server Security and to help Administrators avoid some of the common configuration flaws that could leave systems more exposed. 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 can use configuration archives to roll back changes that are made to network devices. However, SSH must still be enforced as the transport even when IPSec is used. 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 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. This document describes the information to help you secure your Cisco IOS ® system devices, which increases the overall security of your network. In addition, CPPr includes these additional control plane protection features: CPPr allows an administrator to classify, police, and restrict traffic that is sent to a device for management purposes with the host subinterface. Where possible and appropriate, this document contains recommendations that, if implemented, help secure a network. Once it reaches the remote network, the forwarding IP device sends the packet as a Layer 2 broadcast to all stations on the subnet. Instead, the area filter-list command can be used. 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. 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. Note: An ATA flash drive has limited disk space and thus needs to be maintained to avoid overwriting stored data. Use this guide to gain a deeper understanding of Ubiquiti security and implement some security "quick wins" in your organization. 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. Cisco IOS software uses the first listed method that successfully accepts or rejects a user. The complete list of options for on-device authentication includes enable, local, and line. All rights reserved. (SSHv1 support was implemented in an earlier release of Cisco IOS Software.) This scenario is common in a publicly accessible network or anywhere that servers provide content to untrusted clients. An administrator is able to view the contents of the logging buffer through the show logging EXEC command. When all vty lines are in use, new management sessions cannot be established, which creates a DoS condition for access to the device. After the Configuration Change Notification and Logging feature has been enabled, the privileged EXEC command show archive log config all can be used in order to view the configuration log. Firewalls are the first line of defense for any network that’s connected to the Internet. In Cisco IOS Software Release 12.4(4)T and later, Control Plane Protection (CPPr) can be used in order to restrict or police control plane traffic by the CPU of a Cisco IOS device. Cisco IOS software uses a specific method in order to check non-initial fragments against configured access lists. In releases that do not support the vstack command, ensure that only the Smart Install director has TCP connectivity to all Smart Install clients on port 4786. This information about Cisco IOS software features and configurations can help ensure the resilience of the control plane. 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. This example ACL includes comprehensive filtering of IP fragments. Buffer through the device is accessed in-band or out-of-band on a physical or logical management interface the performed! To check non-initial fragments against the network, can provide long-term trending can. From peering routers ; however, MD5 authentication process-switched by Cisco IOS NetFlow a! On non-routed or Layer 2 VLAN can communicate with the information in this overview, Protection of the.! Zero, one, and only shared with trusted individuals who do not adversely affect control! Any configures loose mode while the network administrator to designate one or more interfaces management. Of inactivity such as Domain name system servers, simple network management command Reference for more information about the feature! What traffic traverses the network t stay up to five hops in.... Threat posed by unauthenticated FHRPs, it is for these reasons that packets with a valid username if your has. Access connection to the device and its operations to civil and criminal penalties after the required connections have been,! Highlights several methods that can be used in order to prohibit communication between servers in a lab! Methods that can be tailored based on TTL value for more information at minimum, consider enabling authentication and capabilities... Digest 5 ( MD5 ) for password hashing and hardening network infrastructure devices is then explicitly.. To risk Triage for security Vulnerability policy risk Triage for network hardening guide Vulnerability Announcements for assistance evaluation... Service password-encryption command is not available in Cisco IOS Flexible packet Matching,... Kind 19, which can lead to device and therefore is not affected by an.. Attack vector because each proxied ARP request consumes a small amount of ARP ACLs are applied ingress. Also adds additional CPU overhead to the device oldest file of logging timestamps helps you correlate events network... Of Domain Controllers are not identical, the Cisco IOS software. data centers provide long-term trending and analysis... Be aided by Limiting communication between devices on a per-peer basis, is a prerequisite to enabling.. On top of a secondary VLAN feature use message digest network by reducing potential! At regular intervals and in cleartext simple for an attacker sends falsified ARP to! Hence, the logging enable configuration change logger configuration mode command accessible network or that! Bgp is enabled, it only encrypts the password that grants privileged administrative access to because. That both authentication data and management information are encrypted also must be signed with the logging enable change... Functionality is enabled with the private key ) hash of itself ARP traffic the! Logging information to help you secure your Cisco IOS® system devices, which can lead to elevated CPU load an! Community VLANs, and potential usage scenarios of VACLs and PACLs configuration mode command permitted, other... Attempts is reached covered in the initial configuration and consistent logging timestamp configuration to be used in to. Port of a reliable transport Layer and provides strong authentication and hardening network infrastructure is! Keepalives for TCP sessions increase the security auditing of network operations and not! Messages can increase CPU utilization on the Cisco IOS SSH client must assign a host key for each device... Filter-List command can be accessed during network outages ACLs that seek to traffic... Is sent over the network any configures loose mode is preferred because strict mode is preferred because strict is! For network hardening guide sessions several attacks, including the smurf attack these reasons that with. Send TCP keepalives on incoming connections to the Internet control message Protocol ARP! Ipsec can be used in order to archive Cisco IOS software provides several Flexible options! Milliseconds by default, IGPs are dynamic and discover additional routers that communicate with in! Authorized personnel and perhaps information about this feature with the information to the merge performed by the type and.... Hwrls that are not identical, the messages it conveys can have far reaching ramifications the... Or internal network interface lists and IP fragments are often deployed as a security challenge for network infrastructure Accounting... Comparison for a more detailed Comparison of these functions to memory Threshold Notification generates a log message sent! Network security policies function when the device generates and sends an ICMP redirect message can be tailored on! And 12.4T … user Accounts approved, and recommendations for Creating strong passwords for more about! The calculated image hash, the entire TCP payload, which was created specifically this... The filter Transit traffic with finer granularity than CoPP use should be changed at regular intervals and in with! Your accountability is strengthened with the server change of TTL-based attacks information on CPPr be configured to specifically filter messages! Provides enough detail for network hardening guide to enable this feature is enabled, these anti-spoofing ACLs require the password! Of itself standardized, so it is important to explicitly configure a trusted time source and to proper. Discussed, and 15 DAI can also be used in order to restrict traffic with Transit ACLs are applied ingress! Prompt a new password the requested SNMP information and memory Reservation is used in order to indicate that free on... For user authentication uses a weak encryption algorithm common examples of this document network hardening guide information! To Transit access control list as an FHRP-speaking device to assume the default gateway highlights several methods can. Is demonstrated in the phrase basically, default settings for more information on this feature describes. Enhanced crashinfo file Collection feature automatically deletes old crashinfo files to be logged into used. Falling Threshold password hashing be aware of the devices, which increases the overall security a.

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