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Transcript of Network security
Trish Miller
Network Network SecuritySecurity
Trish Miller
• Types of Attacks
• Attacks on the OSI & TCP/IP Model
• Attack Methods
• Prevention
• Switch Vulnerabilities and Hacking
• Cisco Routers
• Interesting links
Objectives
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• Physical Access Attacks– Wiretapping– Server Hacking– Vandalism
• Dialog Attacks– Eavesdropping– Impersonation– Message Alteration
Types of Attacks
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• Social Engineering– Opening Attachments– Password Theft– Information Theft
Types of Attacks (Cont.)
• Penetration Attacks– Scanning (Probing)– Break-in– Denial of Service– Malware
• Viruses• Worms
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Risk Analysis of the Attack
• What is the cost if the attack succeeds?• What is the probability of occurrence?• What is the severity of the threat?• What is the countermeasure cost?• What is the value to protect the system• Determine if the countermeasure should be
implemented.• Finally determine its priority.
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OSI & TCP/IP Related Attacks
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• Session– Password theft– Unauthorized Access
with Root permission
• Transport & Network:– Forged TCP/IP
addresses– DoS Attacks
OSI Model Related Attacks
• Application layer:– Attacks on web– Attacks are typically
virus
• Presentation: – Cracking of encrypted
transmissions by short encryption key
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• Data Link & Physical– Network Sniffers– Wire Taps– Trojan Horses– Malicious code
OSI Model Related Attacks
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Attacks Related to TCP Packet
• Port Number
– Applications are identified by their Port numbers
– Well-known ports (0-1023)
• HTTP=80, Telnet=23, FTP=21 for supervision, 20 for data transfer, SMTP=25
– Allows applications to be accessed by the root user
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• IP address spoofing
– Change the source IP address
– To conceal identity of the attacker
– To have the victim think the packet comes from a trusted host
– LAND attack
Attacks Related to TCP Packet
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Attacks Related to TCP Packet
• Port Number
– Registered ports (1024-49152) for any application
– Not all operating systems uses these port ranges, although all use well-known ports
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Attack Methods
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• Host Scanning
• Network Scanning
• Port Scanning
• Fingerprinting
Attack Methods
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• Host Scanning– Ping range of IP addresses or use
alternative scanning messages– Identifies victims– Types of Host scanning
• Ping Scanning• TCP SYN/ACK attacks
Attack Methods (Cont.)
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• Network Scanning
– Discovery of the network infrastructure (switches, routers, subnets, etc.)
– Tracert and applications similar identifies all routers along the route to a destination host
Attack Methods (Cont.)
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• Port Scanning– Once a host is identified, scan all ports to find
out if it is a server and what type it is– Two types:
• Server Port Scanning– TCP– UDP
• Client Port Scanning– NetBIOS– Ports 135 – 139 used for NetBIOS ports used for file
and print services.– GRC.com a free website that scan your pc for open
ports.
Attack Methods (Cont.)
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• Fingerprinting– Discovers the host operating system and
applications as well as the version• Active (sends)• Passive (listen)
– Nmap does all major scanning methods
Attack Methods (Cont.)
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• Denial-of-Service (DoS) Attacks– Attacks on availability
– SYN flooding attacks overload a host or network with connection attempts
– Stopping DoS attacks is very hard.
Attack Methods (Cont.)
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• The Break-In
– Password guessing
– Take advantage of unpatched vulnerabilities
– Session hijacking
Attack Methods (Cont.)
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• Download rootkit via TFTP
• Delete audit log files
• Create backdoor account or Trojan backdoor programs
After the Compromise
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• Weaken security
• Access to steal information, do damage
• Install malicious software (RAT, DoS zombie, spam relay, etc.)
After the Compromise (Cont.)
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Prevention
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Preventions
• Stealth Scanning• Access Control• Firewalls• Proxy Servers
• IPsec• Security Policies• DMZ• Host Security
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• Noisiness of Attacks
• Exposure of the Attacker’s IP Address
• Reduce the rate of Attack below the IDS Threshold
• Scan Selective Ports
Stealth Scanning
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• The goal of access control is to prevent attackers from gaining access, and stops them if they do.
• The best way to accomplish this is by: – Determine who needs access to the resources
located on the server.– Decide the access permissions for each resource. – Implement specific access control policies for each
resource. – Record mission critical resources.– Harden the server against attacks.– Disable invalid accounts and establish policies
Access Control
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Firewalls
• Firewalls are designed to protect you from outside attempts to access your computer, either for the purpose of eavesdropping on your activities, stealing data, sabotage, or using your machine as a means to launch an attack on a third party.
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Firewalls (Cont.)
• Hardware– Provides a strong
degree of protection from the outside world.
– Can be effective with little or no setup
– Can protect multiple systems
• Software– Better suite to protect
against Trojans and worms.
– Allows you to configure the ports you wish to monitor. It gives you more fine control.
– Protects a single system.
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Firewalls
• Can Prevent– Discovery
• Network • Traceroute
– Penetration• Synflood • Garbage • UDP Ping• TCP Ping• Ping of Death
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Proxy
• A proxy server is a buffer between your network and the outside world.
• Use an anonymous Proxy to prevent attacks.
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IPSec
• Provides various security services for traffic at the IP layer
• These security services include– Authentication – Integrity– Confidentiality
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IPsec overview - how IPsec helpsProblem How IPsec
helpsDetails
Unauthorized system access
Authentication, tamperproofing
Defense in depth by isolating trusted from untrusted systems
Targeted attacks of high-value servers
Authentication, tamperproofing
Locking down servers with IPsec. Examples: HR servers, Outlook® Web Access (OWA), DC replication
Eavesdropping Authentication, confidentiality
Defense in depth against password or information gathering by untrusted systems
Government guideline compliance
Authentication, confidentiality
Example: “All communications between financial servers must be encrypted.”
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DMZ Image
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• Hardening Servers
• Cisco IOS
• Upgrades and Patches
• Unnecessary Services
• Network Monitoring tools
Host Security
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Switch Vulnerabilities and Hacking
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• Used to locate IP address, version, and model.
• Mass amounts of packets being sent can fake a crash
• Used to troubleshoot network, but should be disabled.
CDP Protocol
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• Give users data by poisoning ARP cache of end node.
• MAC address used to determine destination. Device driver does not check.
• User can forge ARP datagram for man in the middle attack.
ARP Poisoning
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• SNMP manages the network.• Authentication is weak. Public and
Private community keys are clear text.• Uses UDP protocol which is prone to
spoofing.• Enable SNMPv3 without backwards
compatibility.
SNMP
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• Standard STP takes 30-45 seconds to deal with a failure or Root bridge change.
• Purpose: Spanning Tree Attack reviews the traffic on the backbone.
Spanning Tree Attacks
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• Only devices affected by the failure notice the change
• The attacker can create DoS condition on the network by sending BPDUs from the attacker.
Spanning Tree Attacks
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• STEP 1: MAC flood the access switch
• STEP 2: Advertise as a priority zero bridge.
Spanning Tree Attacks (Cont.)
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Spanning Tree Attacks (Cont.)
• STEP 3: The attacker becomes the Root bridge!– Spanning Tree recalculates.– The backbone from the original network is
now the backbone from the attacking host to the other switches on the network.
Spanning Tree Attacks (Cont.)
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• Disabling STP can introduce another attack.
• BPDU Guard– Disables ports using portfast upon
detection of a BPDU message on the port.
– Enabled on any ports running portfast
STP Attack Prevention
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• Root Guard– Prevents any ports that can become the
root bridge due to their BPDU
STP Attack Prevention
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• Cisco Content Switching Modules
• Cisco Content Switching Module with SSL
CSM and CSM-S
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• Cisco Secure Desktop– 3 major vulnerabilities
• Maintains information after an Internet browsing session. This occurs after an SSL VPN session ends.
• Evades the system via the system policies preventing logoff, this will allow a VPN connection to be activated.
• Allow local users to elevate their privileges.
CDM
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• Prevention– Cisco has software to address the
vulnerabilities.– There are workarounds available to mitigate
the effects of some of these vulnerabilities.
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Cisco Routers
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• Two potential issues with Cisco Routers– Problems with certain IOS software– SNMP
Cisco Routers
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• Devices running Cisco IOS versions 12.0S, 12.2, 12.3 or 12.4– Problem with the software – Confidential information can be leaked out – Software updates on the CISCO site can fix
this problem
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•Virtual Private Networks
Virtual connection 1
Virtual Connection 2
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•Virtual Private Networks
Information leak
ErrorConnection
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• Cisco uBR10012 series devices automatically enable SNMP read/write access
• Since there are no access restrictions on this community string , attackers can exploit this to gain complete control of the device
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CISCO Router
AttackingComputer
By sending an SNMP set request with a spoofed source IP address the attacker will be able to get the Victim router to send him its configuration file.
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CISCO Router
AttackingComputer
With this information, the remote computer will be able to have complete control over this router
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• Fixes- Software updates available on the CICSO site that will fix the Read/Write problem
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Links
• http://sectools.org/tools2.html
• http://insecure.org/sploits/l0phtcrack.lanman.problems.html
• http://www.grc.com/intro.htm
• http://www.riskythinking.com
• http://www.hidemyass.com/
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References
• http://www.bmighty.com/network/showArticle.jhtml;jsessionid=2YYDWJHHX3FL2QSNDLPSKHSCJUNN2JVN?articleID=202401432&pgno=2
• http://www.juniper.net/security/auto/vulnerabilities/vuln19998.html
• http://www.blackhat.com/presentations/bh-usa-02/bh-us-02-convery-switches.pdf
• http://www.askapache.com/security/hacking-vlan-switched-networks.html
• http://marc.info/?l=bugtraq&m=116300682804339&w=2
• http://www.secureroot.com/security/advisories/9809702147.html
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