|
Table Of Contents
Configuring Additional Security
Configuration Examples for AutoSecure
AutoSecure Configuration Dialogue: Example
security authentication failure rate
AutoSecure
By using a single command-line interface (CLI), the AutoSecure feature allows a user to perform the following functions:
•Disable common IP services that can be exploited for network attacks
•Enable IP services and features that can aid in the defense of a network when under attack.
This feature also simplifies the security configuration of a router and hardens the router configuration.
Feature History for AutoSecure
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
• Information About AutoSecure
• Configuration Examples for AutoSecure
Information About AutoSecure
To configure the AutoSecure feature, you should understand the following concepts:
Benefits of AutoSecure
Simplified Router Security Configuration
AutoSecure is valuable to customers without special Security Operations Applications because it allows them to quickly secure their network without thorough knowledge of all the Cisco IOS features.
This feature eliminates the complexity of securing a router by creating a new CLI that automates the configuration of security features and disables certain features enabled by default that could be exploited for security holes.
Enhanced Password Security
AutoSecure provides the following mechanisms to enhance security access to the router:
•The ability to configure a required minimum password length, which can eliminate common passwords that are prevalent on most networks, such as "lab" and "cisco."
To configure a minimum password length, use the security passwords min-length command.
•Syslog messages are generated after the number of unsuccessful attempts exceeds the configured threshold.
To configure the number of allowable unsuccessful login attempts (the threshold rate), use the security authentication failure rate command.
Roll-Back and System Logging Message Support
In Cisco IOS Release 12.3(8)T, support for roll-back of the AutoSecure configuration is introduced. Roll-back enables a router to revert back to its preautosecure configuration state if the AutoSecure configuration fails.
Note Prior to Cisco IOS Release 12.3(8)T, roll-back of the AutoSecure configuration is unavailable; thus, you should always save the running configuration before configuring AutoSecure.
System Logging Messages capture any changes or tampering of the AutoSecure configuration that were applied on the running configuration. That is, more detailed audit trail information is provided when autosecure is executed.
Secure Management Plane
Securing the management plane is one of two focus areas for the AutoSecure feature. (The other focus area is described in the following section, " Secure Forwarding Plane.") Securing the management plane is done by turning off certain global and interface services that can be potentially exploited for security attacks and turning on global services that help mitigate the threat of attacks. Secure access and secure logging are also configured for the router.
Caution If your device is managed by a network management (NM) application, securing the management plane could turn off some services like HTTP server and disrupt the NM application support.
The following subsections define how AutoSecure helps to secure the management plane:
• Disable Per Interface Services
Disable Global Services
After enabling this feature (via the auto secure command), the following global services will be disabled on the router without prompting the user:
•Finger—Collects information about the system (reconnaissance) before an attack. If enabled, the information can leave your device vulnerable to attacks.
•PAD—Enables all packet assembler and disassembler (PAD) commands and connections between PAD devices and access servers. If enabled, it can leave your device vulnerable to attacks.
•Small Servers—Causes TCP and User Datagram Protocol (UDP) diagnostic port attacks: a sender transmits a volume of fake requests for UDP diagnostic services on the router, consuming all CPU resources.
•Bootp Server—Bootp is an insecure protocol that can be exploited for an attack.
•HTTP Server—Without secure-http or authentication embedded in the HTTP server with an associated ACL, the HTTP server is insecure and can be exploited for an attack. (If you must enable the HTTP server, you will be prompted for the proper authentication or access list.)
Note If you are using Security Device Manager (SDM), you must manually enable the HTTP server via the ip http server command.
•Identification Service—An unsecure protocol, defined in RFC 1413, that allows one to query a TCP port for identification. An attacker can access private information about the user from the ID server.
•CDP—If a large number of Cisco Discovery Protocol (CDP) packets are sent to the router, the available memory of the router can be consumed, causing the router to crash.
Caution NM applications that use CDP to discover network topology will not be able to perform discovery.
•NTP—Without authentication or access-control, Network Time Protocol (NTP) is insecure and can be used by an attacker to send NTP packets to crash or overload the router. (If you want to turn on NTP, you must configure NTP authentication using Message Digest 5 (MD5) and the ntp access-group command. If NTP is enabled globally, disable it on all interfaces on which it is not needed.)
•Source Routing—Provided only for debugging purposes, so source routing should be disabled in all other cases. Otherwise, packets may slip away from some of the access control mechanisms that they should have gone through.
Disable Per Interface Services
After enabling this feature, the following per interface services will be disabled on the router without prompting the user:
•ICMP redirects—Disabled on all interfaces. Does not add a useful functionality to a correctly configured to network, but it could be used by attackers to exploit security holes.
•ICMP unreachables—Disabled on all interfaces. Internet Control Management Protocol (ICMP) unreachables are a known cause for some ICMP-based denial of service (DoS) attacks.
•ICMP mask reply messages—Disabled on all interfaces. ICMP mask reply messages can give an attacker the subnet mask for a particular subnetwork in the internetwork.
•Proxy-Arp—Disabled on all interfaces. Proxy-Arp requests are a known cause for DoS attacks because the available bandwith and resources of the router can be consumed in an attempt to respond to the repeated requests that are sent by an attacker.
•Directed Broadcast—Disabled on all interfaces. Potential cause of SMURF attacks for DoS.
•Maintenance Operations Protocol (MOP) service—Disabled on all interfaces.
Enable Global Services
After enabling this feature, the following global services will be enabled on the router without prompting the user:
•The service password-encryption command—Prevents passwords from being visible in the configuration.
•The service tcp-keepalives-in and service tcp-keepalives-out commands—Ensures that abnormally terminated TCP sessions are removed.
Secure Access to the Router
Caution If your device is managed by an NM application, securing access to the router could turn off vital services and may disrupt the NM application support.
After enabling this feature, the following options in which to secure access to the router are available to the user:
•If a text banner does not exist, users will be prompted to add a banner. This feature provides the following sample banner:
Authorized access only
This system is the property of ABC Enterprise
Disconnect IMMEDIATELY if you are not an authorized user!
Contact abc@xyz.com +99 876 543210 for help.
•The login and password (preferably a secret password, if supported) are configured on the console, AUX, vty, and tty lines. The transport input and transport output commands are also configured on all of these lines. (Telnet and secure shell (SSH) are the only valid transport methods.) The exec-timeout command is configured on the console and AUX as 10.
•When the image on the device is a crypto image, AutoSecure enables SSH and secure copy (SCP) for access and file transfer to and from the router. The timeout seconds and authentication-retries integer options for the ip ssh command are configured to a minimum number. (Telnet and FTP are not affected by this operation and remain operational.)
•If the AutoSecure user specifies that their device does not use Simple Network Management Protocol (SNMP), one of the following functionalities will occur:
–In interactive mode, the user is asked whether to disable SNMP regardless of the values of the community strings, which act like passwords to regulate access to the agent on the router.
–In non-interact mode, SNMP will be disabled if the community string is "public" or "private."
Note After AutoSecure has been enabled, tools that use SNMP to monitor or configure a device will be unable to communicate with the device via SNMP.
•If authentication, authorization, and accounting (AAA) is not configured, configure local AAA. Autosecure will prompt users to configure a local username and password on the router.
Log for Security
After this feature is enabled, the following logging options, which allow you to identify and respond to security incidents, are available:
•Sequence numbers and time stamps for all debug and log messages. This option is useful when auditing logging messages.
•Logging messages can be generated for login-related events; for example, the message " Blocking Period when Login Attack Detected" will be displayed when a login attack is detected and the router enters "quiet mode." (Quiet mode means that the router will not allows any login attempts via Telnet, HTTP, or SSH.)
For more information on login system messages, see the Cisco IOS Release 12.3(4)T feature module "Cisco IOS Login Enhancements."
•The logging console critical command, which sends system logging (syslog) messages to all available TTY lines and limits messages based on severity.
•The logging buffered command, which copies logging messages to an internal buffer and limits messages logged to the buffer based on severity.
•The logging trap debugging command, which allows all commands with a severity higher than debugging to be sent to the logging server.
Secure Forwarding Plane
To minimize the risk of attacks on the router forward plane, AutoSecure provides the following functions:
•Cisco Express Forwarding (CEF)—AutoSecure enables CEF or distributed CEF (dCEF) on the router whenever possible. Because there is no need to build cache entries when traffic starts arriving for new destinations, CEF behaves more predictably than other modes when presented with large volumes of traffic addressed to many destinations. Thus, routers configured for CEF perform better under SYN attacks than routers using the traditional cache.
Note CEF consumes more memory than a traditional cache.
•If the TCP intercept feature is available, it can be configured on the router for connection timeout.
•If strict Unicast Reverse Path Forwarding (uRPF) is available, it can be configured on the router to help mitigate problems that are caused by the introduction of forged (spoofed) IP source addresses. uRPF discards IP packets that lack a verifiable IP source address.
•If the router is being used as a firewall, it can be configured for context-based access control (CBAC) on public interfaces that are facing the Internet.
Note At the beginning of the AutoSecure dialogue, you will be prompted for a list of public interfaces
How to Configure AutoSecure
This section contains the following procedures:
• Configuring AutoSecure (required)
• Configuring Additional Security (required)
• Verifying AutoSecure (optional)
Configuring AutoSecure
To configure AutoSecure, you must perform the following tasks.
The auto secure Command
The auto secure command takes you through a semi-interactive session (also known as the AutoSecure dialogue) to secure the management and forwarding planes. This command gives you the option to secure just the management or the forwarding plane; if neither option is selected, the dialogue will ask you to configure both planes.
This command also allows you to go through all noninteractive configuration portions of the dialogue before the interactive portions. The noninteractive portions of the dialogue can be enabled by selecting the optional no-interact keyword.
Caution Although the auto secure command helps to secure a router, it does not guarantee the complete security of the router.
Restrictions
The AutoSecure configuration can be configured at run time or setup time. If any related configuration is modified after AutoSecure has been enabled, the AutoSecure configuration may not be fully effective.
SUMMARY STEPS
1. enable
2. auto secure [management | forwarding] [no-interact | full] [ntp | login | ssh | firewall | tcp-intercept]
DETAILED STEPS
Configuring Additional Security
To enable enhanced security access to your router, perform the following steps:
SUMMARY STEPS
1. enable
2. configure terminal
3. security passwords min-length length
4. enable password {password | [encryption-type] encrypted-password}
5. security authentication failure rate threshold-rate log
DETAILED STEPS
Verifying AutoSecure
To verify that the AutoSecure feature is working successfully, perform the following optional steps:
SUMMARY STEPS
1. enable
2. show auto secure config
DETAILED STEPS
Configuration Examples for AutoSecure
This section provides the following configuration example:
• AutoSecure Configuration Dialogue: Example
AutoSecure Configuration Dialogue: Example
The following example is a sample AutoSecure dialogue. After you enable the auto secure command, the feature will automatically prompt you with a similar dialogue unless you enable the no-interact keyword. (For information on which features are disabled and which features are enabled, see the sections, " Secure Management Plane" and " Secure Forwarding Plane" earlier in this document.)
Router# auto secure
--- AutoSecure Configuration ---
*** AutoSecure configuration enhances the security of the router but it will not make router absolutely secure from all security attacks ***
All the configuration done as part of AutoSecure will be shown here. For more details of why and how this configuration is useful, and any possible side effects, please refer to Cisco documentation of AutoSecure.
At any prompt you may enter '?' for help.
Use ctrl-c to abort this session at any prompt.
Gathering information about the router for AutoSecure
Is this router connected to internet? [no]:y
Enter the number of interfaces facing internet [1]:
Interface IP-Address OK? Method Status
Protocol
FastEthernet0/1 10.1.1.1 YES NVRAM up down
FastEthernet1/0 10.2.2.2 YES NVRAM up down
FastEthernet1/1 10.0.0.1 YES NVRAM up up
Loopback0 unassigned YES NVRAM up up
FastEthernet0/0 10.0.0.2 YES NVRAM up down
Enter the interface name that is facing internet:FastEthernet0/0
Securing Management plane services..
Disabling service finger
Disabling service pad
Disabling udp & tcp small servers
Enabling service password encryption
Enabling service tcp-keepalives-in
Enabling service tcp-keepalives-out
Disabling the cdp protocol
Disabling the bootp server
Disabling the http server
Disabling the finger service
Disabling source routing
Disabling gratuitous arp
Enable secret is either not configured or is same as enable password
Enter the new enable secret:abc123
Configuring aaa local authentication
Configuring console, Aux and vty lines for
local authentication, exec-timeout, transport
Configure SSH server? [yes]:
Enter the domain-name:cisco.com
Configuring interface specific AutoSecure services
Disabling the following ip services on all interfaces:
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
Disabling mop on Ethernet interfaces
Securing Forwarding plane services..
Enabling CEF (it might have more memory requirements on some low end
platforms)
Enabling unicast rpf on all interfaces connected to internet
Configure CBAC Firewall feature? [yes/no]:yes
This is the configuration generated:
no service finger
no service pad
no service udp-small-servers
no service tcp-small-servers
service password-encryption
service tcp-keepalives-in
service tcp-keepalives-out
no cdp run
no ip bootp server
no ip http server
no ip finger
no ip source-route
no ip gratuitous-arps
no ip identd
security passwords min-length 6
security authentication failure rate 10 log
enable secret 5 $1$CZ6G$GkGOnHdNJCO3CjNHHyTUA.
aaa new-model
aaa authentication login local_auth local
line console 0
login authentication local_auth
exec-timeout 5 0
transport output telnet
line aux 0
login authentication local_auth
exec-timeout 10 0
transport output telnet
line vty 0 4
login authentication local_auth
transport input telnet
ip domain-name cisco.com
crypto key generate rsa general-keys modulus 1024
ip ssh time-out 60
ip ssh authentication-retries 2
line vty 0 4
transport input ssh telnet
service timestamps debug datetime localtime show-timezone msec
service timestamps log datetime localtime show-timezone msec
logging facility local2
logging trap debugging
service sequence-numbers
logging console critical
logging buffered
int FastEthernet0/1
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
int FastEthernet1/0
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
int FastEthernet1/1
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
int FastEthernet0/0
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
ip cef
interface FastEthernet0/0
ip verify unicast reverse-path
ip inspect audit-trail
ip inspect dns-timeout 7
ip inspect tcp idle-time 14400
ip inspect udp idle-time 1800
ip inspect name autosec_inspect cuseeme timeout 3600
ip inspect name autosec_inspect ftp timeout 3600
ip inspect name autosec_inspect http timeout 3600
ip inspect name autosec_inspect rcmd timeout 3600
ip inspect name autosec_inspect realaudio timeout 3600
ip inspect name autosec_inspect smtp timeout 3600
ip inspect name autosec_inspect tftp timeout 30
ip inspect name autosec_inspect udp timeout 15
ip inspect name autosec_inspect tcp timeout 3600
access-list 100 deny ip any any
interface FastEthernet0/0
ip inspect autosec_inspect out
ip access-group 100 in
!
end
Apply this configuration to running-config? [yes]:yes
Applying the config generated to running-config
The name for the keys will be:ios210.cisco.com
% The key modulus size is 1024 bits
% Generating 1024 bit RSA keys ...[OK]
Router#
Additional References
The following sections provide references related to AutoSecure.
Related Documents
Standards
MIBs
MIBs MIBs LinkNone
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
RFCs TitleRFC 1918
Address Allocation for Private Internets
RFC 2267
Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing
Technical Assistance
Command Reference
This section documents new commands.
• security authentication failure rate
• security passwords min-length
auto secure
To secure the management and forwarding planes of the router, use the auto secure command in privileged EXEC mode.
auto secure [management | forwarding] [no-interact | full] [ntp | login | ssh | firewall | tcp-intercept]
Syntax Description
Defaults
Autosecure is not enabled.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The auto secure command allows a user to disable common IP services that can be exploited for network attacks by using a single CLI. This command eliminates the complexity of securing a router both by automating the configuration of security features and by disabling certain features that are enabled by default and that could be exploited for security holes.
Caution If you are using Security Device Manager (SDM), you must manually enable the HTTP server via the ip http server command.
This command takes you through a semi-interactive session (also known as the AutoSecure dialogue) in which to secure the management and forwarding planes. This command gives you the option to secure just the management or forwarding plane; if neither option is selected, the dialogue will ask you to configure both planes.
Caution If your device is managed by a network management (NM) application, securing the management plane could turn off vital services and disrupt the NM application support.
This command also allows you to go through all noninteractive configuration portions of the dialogue before the interactive portions. The noninteractive portions of the dialogue can be enabled by selecting the optional no-interact keyword.
Roll-back and System Logging Message Support
In Cisco IOS Release 12.3(8)T, support for roll-back of the AutoSecure configuration is introduced. Roll-back enables a router to revert back to its preautosecure configuration state if the AutoSecure configuration fails.
System Logging Messages capture any changes or tampering of the AutoSecure configuration that were applied on the running configuration.
Note Prior to Cisco IOS Release 12.3(8)T, roll-back of the AutoSecure configuration is unavailable; thus, you should always save the running configuration before configuring AutoSecure.
Examples
The following example shows how to enable AutoSecure to secure only the management plane:
Router# auto secure management
Related Commands
Command Descriptionip http server
Enables the HTTP server on your system, including the Cisco web browser user interface.
show auto secure config
Displays AutoSecure configurations.
security authentication failure rate
To configure the number of allowable unsuccessful login attempts, use the security authentication failure-rate command in global configuration mode. To disable this functionality, use the no form of this command.
security authentication failure-rate threshold-rate log
no security authentication failure-rate threshold-rate log
Syntax Description
threshold-rate
Number of allowable unsuccessful login attempts. The default is 10.
log
Syslog authentication failures if the rate exceeds the threshold.
Defaults
The default number of failed login attempts before a 15-second delay is 10.
Command Modes
Global configuration
Command History
Release Modification12.3(1)
This command was introduced.
12.2(18)S
This command was integrated into Cisco IOS Release 12.2(18)T.
Usage Guidelines
The security authentication failure-rate command provides enhanced security access to the router by generating syslog messages after the number of unsuccessful login attempts exceeds the configured threshold rate. This command ensures that there are not any continuous failures to access the router.
Examples
The following example shows how to configure your router to generate a syslog message after eight failed login attempts:
Router(config)# security authentication failure rate 8 log
Related Commands
security passwords min-length
To ensure that all configured passwords are at least a specified length, use the security passwords min-length command in global configuration mode. To disable this functionality, use the no form of this command.
security passwords min-length length
no security passwords min-length length
Syntax Description
Defaults
Six characters
Command Modes
Global configuration
Command History
Release Modification12.3(1)
This command was introduced.
12.2(18)S
This command was integrated into Cisco IOS Release 12.2(18)T.
Usage Guidelines
The security passwords min-length command provides enhanced security access to the router by allowing you to specify a minimum password length, eliminating common passwords that are prevalent on most networks, such as "lab" and "cisco." This command affects user passwords, enable passwords and secrets, and line passwords. After this command is enabled, any password that is less than the specified length will fail.
Examples
The following example shows both how to specify a minimum password length of six characters and what happens when the password does not adhere to the minimum length:
Router(config)# security password min-length 6
Router(config)# enable password lab
% Password too short - must be at least 6 characters. Password not configured.
Related Commands
Command Descriptionenable password
Sets a local password to control access to various privilege levels.
Configures the number of allowable unsuccessful login attempts.
show auto secure config
To display AutoSecure configurations, use the show auto secure config command in privileged EXEC mode.
show suto secure config
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
The following sample output from the show auto secure config command shows what has been enabled and disabled via the auto secure command:
Router# show auto secure config
no service finger
no service pad
no service udp-small-servers
no service tcp-small-servers
service password-encryption
service tcp-keepalives-in
service tcp-keepalives-out
no cdp run
no ip bootp server
no ip http server
no ip finger
no ip source-route
no ip gratuitous-arps
no ip identd
security passwords min-length 6
security authentication failure rate 10 log
enable secret 5 $1$CZ6G$GkGOnHdNJCO3CjNHHyTUA.
aaa new-model
aaa authentication login local_auth local
line console 0
login authentication local_auth
exec-timeout 5 0
transport output telnet
line aux 0
login authentication local_auth
exec-timeout 10 0
transport output telnet
line vty 0 4
login authentication local_auth
transport input telnet
ip domain-name cisco.com
crypto key generate rsa general-keys modulus 1024
ip ssh time-out 60
ip ssh authentication-retries 2
line vty 0 4
transport input ssh telnet
service timestamps debug datetime localtime show-timezone msec
service timestamps log datetime localtime show-timezone msec
logging facility local2
logging trap debugging
service sequence-numbers
logging console critical
logging buffered
interface FastEthernet0/1
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
!
interface FastEthernet1/0
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
!
interface FastEthernet1/1
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
!
interface FastEthernet0/0
no ip redirects
no ip proxy-arp
no ip unreachables
no ip directed-broadcast
no ip mask-reply
no mop enabled
!
ip cef
interface FastEthernet0/0
ip verify unicast reverse-path
ip inspect audit-trail
ip inspect dns-timeout 7
ip inspect tcp idle-time 14400
ip inspect udp idle-time 1800
ip inspect name autosec_inspect cuseeme timeout 3600
ip inspect name autosec_inspect ftp timeout 3600
ip inspect name autosec_inspect http timeout 3600
ip inspect name autosec_inspect rcmd timeout 3600
ip inspect name autosec_inspect realaudio timeout 3600
ip inspect name autosec_inspect smtp timeout 3600
ip inspect name autosec_inspect tftp timeout 30
ip inspect name autosec_inspect udp timeout 15
ip inspect name autosec_inspect tcp timeout 3600
access-list 100 deny ip any any
interface FastEthernet0/0
ip inspect autosec_inspect out
ip access-group 100 in
Related Commands
Copyright © 2004 Cisco Systems, Inc. All rights reserved.
Posted: Thu Feb 10 20:34:24 PST 2005
All contents are Copyright © 1992--2005 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.