• Network+ Guide to Networks6th Edition• Network Security• Objectives• Identify security threats and vulnerabilities in LANs and WANs and design security policies that minimize risks• Explain security measures for network hardware and design, including firewalls, intrusion detection systems, and scanning tools• Understand methods of encryption, such as SSL and IPSec, that can secure data in storage and in transit• Objectives (cont’d.)• Describe how user authentication protocols, such as PKI, RADIUS, TACACS+, Kerberos, CHAP, MS-CHAP, and EAP function• Use network operating system techniques to provide basic security• Understand wireless security protocols, such as WEP, WPA, and 802.11i• Security Assessment• Examine network’s security risks– Consider effects• Different organization– Have different network security risk levels• Posture assessment– Thorough network examination – Determine possible compromise points– Performed in-house by IT staff or performed by a qualified third party agency• Security Risks• Hacker– Individual who gains unauthorized access to systems• Vulnerability– Weakness of a system, process, or architecture that could lead to compromised information or unauthorized access• Exploit– Means of taking advantage of a vulnerability• Zero-day exploit– Taking advantage of undiscovered software vulnerability that has not yet become publicly known– Most vulnerabilities are well known• Risks Associated with People• More than half of all security breaches are caused by human errors and ignorance• Social engineering: manipulating social relationships– Strategy to gain password– Phishing• Glean access, authentication information• Pose as someone needing information• Many risks associated with people exist• Easiest way to circumvent network security– Take advantage of human error• Risks Associated with Transmission and Hardware• Physical, Data Link, and Network layer security risks– Require more technical sophistication• Risks inherent in network hardware and design– Transmission interception• Man-in-the-middle attack– Eavesdropping• Networks connecting to Internet via leased public lines– Sniffing• Repeating devices broadcast traffic over entire segment• Risks Associated with Transmission and Hardware (cont’d.)• Risks inherent in network hardware and design (cont’d.)– Port access via port scanner• Unused switch, router, server ports not secured– Private address availability to outside• Routers not properly configured to mask internal subnets– Router attack• Routers not configured to drop suspicious packets• Risks Associated with Transmission and Hardware (cont’d.)• Risks inherent in network hardware and design (cont’d.)– Access servers not secured and monitored– Computers hosting sensitive data:• May coexist on same subnet as public computers– Insecure passwords• Easily guessable or default values • Risks Associated with Protocols and Software• Includes Transport, Session, Presentation, and Application layers• Networking protocols and software risks– TCP/IP security flaws– NOS back doors, security flaws– Administrators default security options– Intercepting transactions between applications• Risks Associated with Internet Access• Network security compromise– More often “from the inside”• Outside threats still very real– Web browsers may contain a but that permit scripts to access systems while they are connected to the Internet– Users provide information to sites which may be captured and used to break into a system• Risks Associated with Internet Access (cont’d.)• Common Internet-related security issues– Improperly configured firewall• Outsiders obtain internal IP addresses: IP spoofing– Telnets or FTPs• Transmit user ID and password in plain text– Information on newsgroups, mailing lists, forms• Provide hackers user information– Chat session flashing– Denial-of-service attack• Smurf attack: hacker issues flood of broadcast ping messages• An Effective Security Policy• Minimize break-in risk– Communicate with and manage users– Use thoroughly planned security policy• Security policy
– Identifies security goals, risks, authority levels, designated security coordinator, and team members
– Responsibilities of each employee
– Specifies how to address security breaches
• Security Policy Goals
• Typical Security Policy Goals:
– Ensure authorized users have appropriate resource access
– Prevent unauthorized user access
– Protect unauthorized sensitive data access
• Inside and outside
– Prevent accidental hardware and software damage
– Prevent intentional hardware or software damage
– Create secure environment
• Withstand, respond to, and recover from threat
– Communicate employees’ responsibilities
• Security Policy Goals (cont’d.)
• Strategy to attain your security goals
– Form committee
• Involve as many decision makers as possible
• Assign security coordinator to drive policy creation
– Understand risks
• Conduct posture assessment
• Rate severity and likelihood of each threat
– Assign person responsible for addressing threats
• Security Policy Content
• Outline policy content
– Define policy subheadings
• Explain to users:
– What they can and cannot do
– How measures protect network’s security
• Response Policy
• Security breach occurrence
– Provide planned response
• Identify response team members
– Understand security policy, risks, and measures in place
– Accept role with certain responsibilities
– Regularly rehearse defense
• Threat drill
• Response Policy (cont’d.)
• Suggested team roles
– Dispatcher
• Person on call; first to notice; alerted to problem
– Manager
• Coordinates resources
– Technical support specialist
• One focus: solve problem quickly
– Public relations specialist
• Official spokesperson to public
• After problem resolution
– Review what happened and how it can be prevented
• Physical Security
• Restrict physical access to network components
– Lock computer rooms, telco rooms, wiring closets, and equipment cabinets
• Locks can be physical or electronic
– Electronic access badges
– Locks requiring entrants to punch numeric code
– Bio-recognition access: identifies individual’s by their unique physical characteristics, such as the color patter in their iris or the geometry of their hand, to verify their identity
• Physical Security (cont’d.)
• Physical barriers
– Gates, fences, walls, and landscaping
• Closed-circuit TV systems monitor secured rooms
• Surveillance cameras
– Data centers, telco rooms, data storage areas, facility entrances
– Central security office capabilities
• Display several camera views at once
• Switch from camera to camera
– Video footage used in investigation and prosecution
• Physical Security (cont’d.)
• Consider losses from salvaged and discarded computers
– Hard disk information stolen
– Solutions
• Run specialized disk sanitizer program
• Remove disk and use magnetic hard disk eraser
• Pulverize or melt disk
• Security in Network Design
• Breaches may occur due to poor LAN or WAN design
– Address though intelligent network design
• Preventing external LAN security breaches from affecting your network is a matter of restricting access at every point where LAN connects to rest of the world
• Router Access Lists
• Control traffic through routers
• Router’s main functions
– Examine packets
– Determine destination
• Based on Network layer addressing information
• ACL (access control list)
– Also called access list
– Routers can decline to forward certain packets
• Router Access Lists (cont’d.)
• ACL variables used to permit or deny traffic
– Network layer protocol (IP, ICMP)
– Transport layer protocol (TCP, UDP)
– Source IP address
– Source netmask
– Destination IP address
– Destination netmask
– TCP or UDP port number
• Router Access Lists (cont’d.)
• Router receives packet, examines packet
– Refers to ACL for permit, deny criteria
– Drops packet if deny characteristics match
– Forwards packet if permit characteristics match
• Access list statement examples
– Deny all traffic from source address with netmask 255.255.255.255
– Deny all traffic destined for TCP port 23
• Separate ACL’s for:
– Interfaces; inbound and outbound traffic
• Intrusion Detection and Prevention
• Proactive security measure
– Detecting suspicious network activity
• IDS (intrusion detection system)
– Software monitoring traffic
• Port mirroring
– One port makes copy of traffic to a second port which monitors the traffic
• Intrusion Detection and Prevention (cont’d.)
• IDS software detects many suspicious traffic patterns
– Examples: denial-of-service, smurf attacks
• IDS can only detect and log suspicious activity
• Intrusion Detection and Prevention (cont’d.)
• IPS (intrusion-prevention system)
– Reacts to suspicious activity when alerted
– Detects threat and prevents traffic from flowing to network
• Based on originating IP address
• HIDS (host intrusion detection system) runs on a client or server and monitors operating system files for unauthorized changes, failed logon attempts, etc.
• NIDS (network intrusion detection system) device or system designed to monitor network traffic at a network entry point, such as a firewall—watches for suspicious traffic patterns
• Firewalls
• Specialized device or computer installed with specialized software
– Selectively filters and blocks traffic between networks
– Involves hardware and software combination
• Firewall location
– Between two interconnected private networks
– Between private network and public network (network-based firewall)
• Firewalls (cont’d.)
• Packet-filtering firewall
– Simplest firewall
– Examines header of every entering packet
– Can block traffic entering or exiting a LAN
• Firewall d
đang được dịch, vui lòng đợi..
![](//viimg.ilovetranslation.com/pic/loading_3.gif?v=b9814dd30c1d7c59_8619)