Command:  no logging console - or - logging console critical, Best practice: Check if state of event logging on the firewall is enabled. Reply. Control plane functions consist of the protocols and processes that communicate between network devices to move data from source to destination. Here are a list of best practices that can be applied to a Cisco ASA. Command:  aaa accounting command EXAUTH LOCAL, Best practice: Authenticates users who access privileged EXEC mode when they use the enable command. When the Botnet Traffic Filter feature is enabled, the Cisco ASA compares DNS A-records and CNAME records against the domain names in the database. Note: MD5 is the recommended configuration for ospf authentication,  ! Because the data plane is responsible for processing and forwarding traffic, protecting the firewall data plane plays an important part in firewall hardening and security. The following configuration example includes the configuration of a logging buffer of 16,384 bytes and a severity of 6, information, indicating that messages at levels 0 (emergency) through 6 (information) are stored: Refer to Cisco ASA Command Reference for more information about buffered logging. As ACLs grow in length, the time needed to evaluate the ACEs in sequence can also increase. Use the global configuration commands no logging console and no logging monitor to disable logging to the console sessions and terminal lines. The CSC-SSM operates as a content scanning and filtering module. The ICMP inspection engine ensures that there is only one response for each request, and that the sequence number is correct. best practices cisco ACL. Access to the privileged EXEC mode (enable mode) should be protected by requiring a password else user logged in to user mode can access enable mode. On Cisco firewall devices, the console port is an asynchronous line that can be used for local and remote access to a device. It is recommended to authenticate NTP updates so that time is synchronized with approved servers only. When the browser receives the HTTP packets with , it ignores the actual content by assuming that the content contains the author's comments. The ASA allows an administrator to lock out a local user account after a configured number of unsuccessful login attempts. In some legal jurisdictions it may be improbable and/or illegal to monitor and prosecute malicious users unless they have been notified that they are not permitted to use or access a respective device or resource. TACACS+ Authentication           Authentication Fallback           TACACS+ Command Authorization           TACACS+ Command Accounting        Fortifying the Simple Network Management Protocol           SNMP Community Strings           SNMP MIBs           SNMP Version 3        Logging Best Practices           Send Logs to a Central Location           Logging Level           Disable Logging to Monitor Sessions and the Console           Use Buffered Logging           Configure Logging Time Stamps        Software Configuration Management  Securing the Control Plane        General Control Plane Hardening           ICMP Redirects           ICMP Unreachables           Limiting ICMP Responses       Securing Routing Protocols  Routing Protocol Authentication  Securing the Data Plane        General Data Plane Hardening        Filtering Transit Traffic with Transit ACLs           ACL Configuration Best Practices           Security Levels        Content and URL Filtering           Content Filtering           URL Filtering        Modular Policy Framework        Anti-Spoofing Protections           Unicast Reverse Path Forwarding           Antispoofing with Access Lists           Inspection           Enable Inspection for Nondefault Applications           ACLs to Block Private and Bogon Addresses        Denial of Service Protections           Threat Detection           Connection Limiting           TCP Normalizer           Botnet Protection  Limiting the CPU Impact of Data Plane Traffic        Traffic Identification and Traceback           IPv6 Traffic Filtering        High Availability Security        Best Practices Checklist           Management Plane Checks           Control Plane Checks           Data Plane Checks  Conclusion  Acknowledgments  References. If the security appliance is not able to reach the first server in the list, it tries the second server from the list, and so on. The following configuration example builds on the previous TACACS+ authentication example to include fallback authentication to the local database: Refer to the Configuring Management Access section of the Cisco ASA 5500 Series Configuration Guide for more information on the use of fallback authentication with AAA. Many of the segment checks can be controlled by configuring one or more advanced TCP connection settings. If IPv6 traffic is used in the network, an IPv6 ACL can be configured if desired to control the traffic passing through the security appliance. An ACL must be applied to each lower-security interface so that specific inbound connections are permitted. This algorithm has had considerable public review and is not known to be reversible. There are key details that establish a firewall as a firewall and not a Layer 3 forwarding device. The Cisco ASA Botnet Traffic Filter is integrated into all Cisco ASA appliances and inspects traffic traversing the appliance to detect rogue traffic in the network. Also, ICMP generally requires enabling icmp inspection because the ICMP inspection engine allows ICMP traffic to have a "session" so it can be inspected like TCP and UDP traffic. therefore the "message-digest" configuration option should be leveraged. If TACACS+ were to become completely unavailable, each administrator can use a local username and password. ICMP unreachable rate limiting can be changed from the default using the, For details on configuring ICMP unreachables, see. This video is unavailable. The buffered data is available only from an exec or enabled exec session, and it is cleared when the device reboots. As all information between the two firewalls in an HA configuration is sent (in clear text) over the failover/stateful failover link(s), the key to securing the Cisco firewall HA solution is to secure the communication with a failover key. I have been tasked with performing a clean … An administrator must manually configure ACLs to block malicious traffic. These topics contain operational recommendations that administrators and engineers are advised to implement. The ability to configure security levels is a necessary firewall feature. Cisco reserves the right to change or update this document at any time. Although this approach does enhance the accountability of network administrators during TACACS+ outages, it significantly increases the administrative burden because local user accounts on all network devices must be maintained. Refer to. Watch Queue Queue Basic threat detection is enabled by default on all ASA’s running 8.0(2) and later. uRPF in strict mode may drop legitimate traffic that is received on an interface that was not the firewall's choice for sending return traffic. ASA ACL with and without Security Level Hi All, I know that a higher security level can speak to lower security level without an ACL whereas a lower security level cannot speak to a higher security level without an ACL. Søg efter jobs der relaterer sig til Cisco asa acl best practices, eller ansæt på verdens største freelance-markedsplads med 19m+ jobs. Cisco firewalls define a specific interface as being the Management interface. Antispoofing is one such feature, which helps to protect an interface of the ASA by verifying that the source of network traffic is valid. Cisco ASA 5500 Series Adaptive Security Appliances provide reputation-based control for an IP address or domain name. Suspect TCP flags (for example, NULL, SYN/FIN, or FIN/URG). Administrators can define an external filtering server by using the. After centralized logging is implemented, one must develop a structured approach to log analysis and incident tracking. This section lists some best practices to be followed for ACL configuration on firewalls. 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. Receive ACL – The receive path ACL (rACL) feature was developed for Cisco 7500 and Cisco 12000 Series routers as the initial step toward achieving a Cisco IOS-wide route processor protection mechanism. Some command line examples in this document are wrapped to enhance readability. Two inspection engines that should be enabled during installation are ICMP and ICMP error inspection. Earlier releases of Cisco ASA Software may not include all features or capabilities outlined. The Cisco Security Manager platform manages firewall devices and can provide change management and configuration change logging functionality. The Botnet Traffic Filter monitors all ports and performs a real-time lookup in its database of known botnet IP addresses and domain names. Command:  sysopt noproxyarp , Best practice: Preferable to disable ICMP on outside interfaces at a minimum. When internal clients are infected with malware and attempt to phone home across the network, the Botnet Traffic Filter alerts the system administrator of these attempts though the regular logging process for manual intervention. The following are the key points: Note: Users may experience longer access times if the response from the filtering server is slow or delayed. To disable global inspection for an application, use the, For an FTP and TFTP filtering example, see, For more details regarding ICMP inspection, see the. service call-home call-home contact-email-addr customer@mail.server profile CiscoSCH destination address http https://tools.cisco.com/its/service/oddce/services/DDCEService destination transport-method http subscribe-to-alert-group inventory periodic monthly subscribe-to-alert-group configuration periodic monthly ! RFC 2827 (BCP 38) describes uses of access lists as a current best practice to defeat IP source address spoofing. Filtering with an interface access list elicits the transmission of ICMP unreachable messages back to the source of the filtered traffic. Step 1: Identify the traffic to apply connection limits using a class map, ASA(config)# access list CONNS-ACL extended permit ip any 10.1.1.1 255.255.255.255 ASA(config)# class-map CONNS-MAP ASA(config-cmap)# match access-list CONNS-ACL, Step 2: Add a policy map to set the actions to take on the class map traffic, ASA(config)# policy-map CONNS-POLICY ASA(config-pmap)# class CONNS-MAP ! For further details, see the Cisco ASA 5500 Series Configuration Guide in addition to the Resources section of this document. Command:  snmp server enable traps, Best practice: Network Time Protocol (NTP) is a UDP based protocol used to synchronize time clocks amongst network devices. The firewall, through stateful inspection, also monitors the state of the connection to compile information to place in a state table. There is no support for SNMP views. To configure management access for the AIP module, the administrator can use Adaptive Security Device Manager (ASDM), IPS Device Manager (IDM), or the ASA command line via thesession 1 EXEC command. Based on this investigation, the Botnet Traffic Filter will determine whether a connection attempt is benign and should be allowed or whether it is a risk and should be tagged for mitigation. Administrators can enter this command all on one line (in any order) or enter each attribute as a separate command. This is typically employed as an auxiliary technique for countless types of network-based attacks. Through the stateful application inspection used by the Adaptive Security Algorithm, the Cisco ASA tracks each connection that traverses the firewall and ensures that it is valid. Cisco firewalls can delegate packet-filtering responsibilities to an external server. Otherwise, severity level 6 is the default. For more details on Cisco ASA security levels, see the Security Levels section of this document. If NTP is used, it is important to explicitly configure a trusted time source and to use proper authentication. Command:  aaa authentication http console RADIUS LOCAL, Best practice: Before the firewall can authenticate a Telnet or SSH user, we must first configure access to the firewall using the telnet or ssh commands. The no service password-recovery feature prevents anyone with console access from insecurely accessing the device configuration and clearing the password. For details on configuring ICMP unreachables, see icmp unreachable in the Cisco ASA 5500 Series Command Reference. Although most of this document is devoted to the secure configuration of a Cisco firewall device, configurations alone do not completely secure a network. 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. The Adaptive Security Appliance (ASA) is Cisco’s implementation of a dedicated firewall and it truly is an intriguing device. This section discusses some antispoofing features. The firewall application discards segments that appear to be abnormal or malformed. Although it has some similarities (in terms of configuration) with the Cisco IOS, it is actually based on a totally different operating system with unnecessary service entirely stripped away. Refer to, Apply actions to the Layer 3 and Layer 4 traffic. Command:  aaa-server TACACS+ host , Best practice: When you configure the aaa accounting command, each command other than show commands entered by an administrator is recorded and sent to the accounting server or servers. When one unit fails, another immediately takes its place. Any HTTP flow that does not adhere to the basic checks is dropped by default. section of the Cisco ASA 5500 Series Configuration Guide for more information about command authorization. An administrator is able to view the contents of the logging buffer through the show logging EXEC command. The feature will be explained in a manner that allows the security practitioner and decision makers to determine whether the feature is required in a certain environment. Because of the secure nature and operations of Cisco firewall platforms, ICMP responses from the firewall should be limited by filtering traffic to permit only what is necessary or expected. The following shows the complete command syntax: filter activex|java port[- port] except local_ip local_mask foreign_ip foreign_mask. However, note that a locally configured password for privileged access will still be needed in the event of TACACS+ or RADIUS services failure. Any source and destination address specified in the ACL is relative to any address translation that occurs on the interface where the ACL is applied. The following sets connection number limits ASA(config-pmap-c)# set connection {[conn-max n] [embryonic-conn-max n] [per-client-embryonic-max n] [per-client-max n] [random-sequence-number {enable | disable}]}. It is important to configure and use an ACL to limit the types of traffic in a specific direction. An access list may also be specified that permits or denies certain source addresses in uRPF loose mode. Therefore, ACL changes should be made when traffic through the firewall is low. For details on configuring ICMP filtering, see icmp in the Cisco ASA 5500 Series Command Reference. Cisco provides the official information contained on the Cisco Security portal in English only. There are two configuration options that are relevant when configuring buffered logging: the logging buffer size and the message severities that are stored in the buffer. I will add if something else comes to mind and naturally if you have something on your mind do ask more. In addition, if the firewall is managed through an external management tool, it should be able to provide configuration management logs. The ICMP inspection engine allows ICMP traffic to be inspected in the same way as TCP and UDP traffic. It also does not allow users to change the configuration register value and access NVRAM. This is because after possibly years of adding rules to the firewall there are probably alot of rules that could later be made more compact by creating "object-group" for both services and source/destination IP addresses. CLICK HERE. These management users can access the firewall device via SSH, Telnet, HTTP, or HTTPS. These should always be changed to more secure strings. When a request for access to a resource or device is received, the request is challenged for verification of the password and identity. The security of a device should begin with a progression up the Open Systems Interconnection (OSI) reference model, beginning with the physical layer. The. They also maintain a page dedicated to filtering these bogon addresses at The Bogon Reference. Cisco recommends the use of SSH for secure CLI data communication. User snmpv3user2 has an MD5 authentication password ofauthpassword and a Triple Data Encryption Standard (3DES) encryption password of privpassword: Note that snmp-server user configuration commands are not displayed in the configuration output of the device as required by RFC 3414; therefore, the user password is not viewable from the configuration. For more details regarding the TCP Normalizer feature, see the TCP Normalization section of the Cisco ASA 5500 Series Configuration Guide. Generating these messages can increase CPU utilization on the device. The following configuration can be added to the previous AAA authentication example to implement command authorization: Refer to the Configuring Command Authorization section of the Cisco ASA 5500 Series Configuration Guide for more information about command authorization. The firewall application uses TCP normalization to block certain types of network attacks (for example, insertionattacks and evasion attacks). Chapter Description. The Botnet Traffic Filter feature does not automatically block botnet-related traffic. This allows administrators and engineers to apply management traffic-based policies throughout the network. The following example configuration enables AAA command accounting for EXEC commands entered at privilege levels zero, one, and 15. TCP normalization helps protect the Cisco ASA from attacks. Cisco ASA software supports the use of a local log buffer so that an administrator can view locally generated log messages. When DNS snooping is enabled, the Cisco ASA builds a DNS reverse cache (DNSRC) for all the DNS replies received on interfaces where DNS snooping is enabled. When administrators use uRPF in loose mode, the source address must appear in the routing table. Cisco firewall interactive management sessions include console, Telnet, SSH, HTTP, and HTTPS. Event logging provides visibility into the operation of a Cisco ASA device and the network where it is deployed. It is not recommended to access the security appliance through an HTTP-based GUI session. As such, the messages it conveys can have far-reaching ramifications to the TCP and IP protocols in general. Cisco firewalls can be configured to elicit or suppress ICMP unreachable messages. ICMP unreachables should be filtered to allow only known sources, for example those from management subnets. This RFC is a widespread resource, particularly for the Internet edge, because in such an environment the boundary between private and public addresses (in the sense of RFC 1918) is clearly demarcated. Ensure that the date/time is correctly set (if NTP is not configured) so that the timestamps provide the proper day/time of the log messages. In this scenario, in addition to having the firewall placed in a restricted-access room, the firewall may also be housed in a locking rack/sector in the restricted room. Average(eps) Current(eps) Trigger Total events. The ability to configure security levels is a necessary firewall feature. ICMP unreachable message generation can be disabled using the global configuration command icmp deny any unreachable . When all sessions are in use, new management sessions cannot be established, creating a DoS condition for access to the device. The method for communication of less-severe issues is the Cisco Security Response. Note that authorized users can lock themselves out of a device if the number of unsuccessful login attempts is reached. The ability to understand device hardening at the core of security architecture design and implementation is essential to success. One must be aware that the console port on Cisco firewall devices has special privileges. When the user enters EXEC commands, the Cisco ASA sends each command to the configured AAA server. Note that the Management interfaces on a Cisco firewall use the global routing table of the device; they do not use a separate routing table. An ACL must be applied to each lower-security interface so that specific inbound connections are permitted. The MD5 keyed digest in each EIGRP packet prevents the introduction of unauthorized or false routing messages from unapproved sources. User passwords are also hashed using the MD5 algorithm after they have been concatenated with a salt value that provides resilience against dictionary attacks. Some applications require special handling in the Adaptive Security Algorithm firewall application inspection function. However, doing so can elevate the CPU load of a Cisco ASA device and therefore is not recommended. To set the maximum connections (both TCP and UDP), maximum embryonic connections, per-client-embryonic-max, or per-client-max, or to indicate whether to disable TCP sequence randomization, administrators can enter this command: Recall that the per-client-max and per-client-embryonic-max is an integer from 0 through 65535 and the default is 0, which means no limit on connections. Thanks for your response, I will be reconfiguring the ASA using the ASDM (Easier and quicker for me). The administrator decides which MIB object ID (OID) to poll and which SNMP traps to enable to monitor the uninterrupted operation of the firewall device. For more details regarding security levels, see the, Cisco firewalls can delegate packet-filtering responsibilities to an external server. Those are just some things that came to my mind. To enhance security, routing updates may be authenticated using a simple password or keys depending on the routing protocol being used. When administrators use uRPF in loose mode, the source address must appear in the routing table. uRPF in strict mode may drop legitimate traffic that is received on an interface that was not the firewall's choice for sending return traffic. In ROMMON mode, the device software can be reloaded to prompt a new system configuration that includes a new password. Using the information in a log, the administrator can tell whether the firewall is working properly or whether it has been compromised.