Cisco Router Security
description
Transcript of Cisco Router Security
Cisco Router Forensics
Thomas Akin, CISSPDirector, Southeast Cybercrime Institute
Kennesaw State UniversityBlackHat Briefings, USA, 2002
Hacking Cisco
Cisco Bugtraq Vulnerabilities
• 1998 - 3• 1999 - 5• 2000 - 23• 2001 - 46• 2002 (est) - 94
Hacking Routers
Example Exploits:• HTTP Authentication Vulnerability
– using a URL of http://router.address/level/$NUMBER/exec/.... where $NUMBER is an integer between 16 and 99, it is possible for a remote user to gain full administrative access.
• NTP Vulnerability– By sending a crafted NTP control packet, it is possible to trigger a buffer overflow in the
NTP daemon
• SNMP Parsing Vulnerability– Malformed SNMP messages received by affected systems can cause various parsing and
processing functions to fail, which results in a system crash and reload. In some cases, access-list statements on the SNMP service do not protect the device
Hacking Routers
When a router is hacked it allows an attacker to
• DoS or disable the router & network…
• Compromise other routers…
• Bypass firewalls, IDS systems, etc…
• Monitor and record all outgoing an incoming traffic…
• Redirect whatever traffic they desire…
Cisco Routers in a Nutshell
Flash• Persistent• Holds
– Startup configuration
– IOS files
RAM• Non-Persistent• Holds
– Running configuration
– Dynamic tables (i.e)• Arp
• Routing
• NAT
• ACL violations
• Protocol Statistics
• Etc…
Router Forensics v/s Traditional Forensics
Traditional Forensics• Immediately shutdown
the system (or pull the power cord)
• Make a forensic duplicate
• Perform analysis on the duplicate
• Live system data is rarely recovered.
Router Forensics• Live system data is the
most valuable.• Immediate shutdown
destroys all of this data.• Persistent (flash) data
will likely be unchanged and useless.
• Investigators must recover live data for analysis
Computer Forensics: The Unholy Grail
The goal is to “catch the criminal behind the keyboard.” Not to find fascinating computer evidence.
Computer evidence is never the smoking gun. Most often computer evidence either
• Provides leads to other evidence…
• Corroborates other evidence…
Chain of Custody
Detailed, Methodical, Unquestionable….• Where you received the evidence…
• When you received the evidence…
• Who you received the evidence from…
• What your seizure methods were…
• Why you seized the evidence…
• How you maintained your chain of custody…
Example CoC Form
Example CoC Form
Incident Response
• DO NOT REBOOT THE ROUTER.
• Change nothing, record everything.
• Before you say it is an accident, make sure it isn’t an incident…
• Before you say it is an incident, make sure it isn’t an accident…
Accessing the Router
DO• Access the router
through the console• Record your entire
console session• Run show commands• Record the actual time
and the router’s time• Record the volatile
information
DON’T• REBOOT THE
ROUTER• Access the router
through the network• Run configuration
commands• Rely only on persistent
information
Recording Your Session
• Always start recording your session before you even log onto the router
• Frequently show the current time with the show clock detail command
Volatile EvidenceDirect Access
• show clock detail• show version• show running-config• show startup-config• show reload• show ip route• show ip arp• show users• show logging
• show ip interface• show interfaces• show tcp brief all• show ip sockets• show ip nat translations
verbose• show ip cache flow• show ip cef• show snmp user• show snmp group• show clock detail
Volatile Evidence Indirect Access
Remote evidence may be all you can get if the passwords have been changed…
• Port scan each router IPnmap -v -sS -P0 -p 1- Router.domain.comnmap -v -sU -P0 -p 1- Router.domain.comnmap -v -sR -P0 -p 1- Router.domain.com
• SNMP scan each router IPsnmpwalk –v1 Router.domain.com publicsnmpwalk –v1 Router.domain.com private
Intrusion Analysis
• IOS Vulnerabilities
• Running v/s Startup configurations
• Logging
• Timestamps
Logging
• Console LoggingThese will be captured by recording your session.
• Buffer LoggingIf buffered logging is turned on, the show logging command will show you the contents of the router log buffer, what level logging is performed at, and what hosts logging is sent to.
• Terminal LoggingThis allows non console sessions to view log messages.
• Syslog LoggingLog messages are sent to a syslog server when logging is turned on and the logging servername command is set.
Logging
• SNMP loggingIf SNMP is running, SNMP traps may be sent to a logging server.
• AAA LoggingIf AAA is running the check the aaa accounting commands to see what logging is being sent to the Network Access Server.
• ACL Violation LoggingACL can be configured to log any packets that match their rules by ending the ACL with the log or log-input keywords. These log messages are sent the the routers log buffer and to the syslog server.
Real Time Forensics
After removing or collecting information from your compromised router you can use the router to help monitor the network and itself by turning on logging if it wasn’t previously.
Router#config terminal
Router(config)#service timestamps log datatime msec \ localtime show-timezone
Router(config)#no logging console
Router(config)#logging on
Router(config)#logging buffered 32000
Router(config)#logging buffered informational
Router(config)#logging facility local6
Router(config)#logging trap informational
Router(config)#logging Syslog-server.domain.com
Real Time Forensics
Using AAA provided even greater ability to log information. TACACS+ even allows you to log every command executed on the router to your Network Access Server
Router#config terminal
Router(config)#aaa accounting exec default start-stop \ group tacacs+
Router(config)#aaa accounting system default stop-only \ group tacacs+
Router(config)#aaa accounting connection default \ start-stop group tacacs+
Router(config)#aaa accounting network default \ start-stop group tacacs+
Real Time Forensics
You can also use ACL logging to count packets and log specific events. By configuring syslog logging and analyzing your syslog files in real time you can perform real time monitoring
• The ACLaccess-list 149 permit tcp host 130.18.59.1 any eq \ 161 log-inputwill not block any packets, but will log all incoming SNMP requests from 130.18.59.1 to any internal host.
• The ACLsaccess-list 148 deny tcp 130.18.59.0 0.0.0.255 any \ eq 53 log-inputaccess-list 148 deny udp 130.18.59.0 0.0.0.255 any \ eq 53 log-inputwill block and log any DNS packets from the subnet 130.18.59.0/24 to any internal host.
Summary
• Hacking Cisco Routers• Router Hardware & Software• Router Forensics v/s Traditional Forensics• Computer Evidence & Chain of Custody• Incident Response• Accessing the Router• Gathering volatile evidence—internal & external• Gathering logging evidence• Performing Real Time Network Forensics
Thank you!
Thomas Akin
http://cybercrime.kennesaw.edu
On you conference CD you will find:
• A copy of this presentation
• A router forensics checklist
• A sample Chain of Custody form
• A sample Evidence Receipt tag