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1 Securing the Network Infrastructure. Objectives Work with the network cable plant Secure removable media Harden network devices Design network topologies.

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Presentation on theme: "1 Securing the Network Infrastructure. Objectives Work with the network cable plant Secure removable media Harden network devices Design network topologies."— Presentation transcript:

1 1 Securing the Network Infrastructure

2 Objectives Work with the network cable plant Secure removable media Harden network devices Design network topologies 2

3 Working with the Network Cable Plant Cable plant: physical infrastructure of a network (wire, connectors, and cables) used to carry data communication signals between equipment Three types of transmission media: Coaxial cables Twisted-pair cables Fiber-optic cables 3

4 Coaxial Cables Coaxial cable was main type of copper cabling used in computer networks for many years Has a single copper wire at its center surrounded by insulation and shielding Called coaxial because it houses two (co) axes or shaftsthe copper wire and the shielding Thick coaxial cable has a copper wire in center surrounded by a thick layer of insulation that is covered with braided metal shielding 4

5 Coaxial Cables (continued) Thin coaxial cable looks similar to the cable that carries a cable TV signal A braided copper mesh channel surrounds the insulation and everything is covered by an outer shield of insulation for the cable itself The copper mesh channel protects the core from interference BNC connectors: connectors used on the ends of a thin coaxial cable 5

6 Coaxial Cables (continued) 6 Sheath Braided Sheilding Insulation (PVC, Teflon) Conducting Core

7 Twisted-Pair Cables Standard for copper cabling used in computer networks today, replacing thin coaxial cable Composed of two insulated copper wires twisted around each other and bundled together with other pairs in a jacket Shielded twisted-pair (STP) cables have a foil shielding on the inside of the jacket to reduce interference Unshielded twisted-pair (UTP) cables do not have any shielding Twisted-pair cables have RJ-45 connectors 7

8 Fiber-Optic Cables Coaxial and twisted-pair cables have copper wire at the center that conducts an electrical signal Fiber-optic cable uses a very thin cylinder of glass (core) at its center instead of copper that transmit light impulses A glass tube (cladding) surrounds the core The core and cladding are protected by a jacket 8

9 Fiber-Optic Cables (continued) Classified by the diameter of the core and the diameter of the cladding Diameters are measured in microns, each is about 1/25,000 of an inch or one-millionth of a meter Two types: Single-mode fiber cables: used when data must be transmitted over long distances Multimode cable: supports many simultaneous light transmissions, generated by light-emitting diodes 9

10 Securing the Cable Plant Securing cabling outside the protected network is not the primary security issue for most organizations Focus is on protecting access to the cable plant in the internal network An attacker who can access the internal network directly through the cable plant has effectively bypassed the network security perimeter and can launch his attacks at will 10

11 Securing the Cable Plant (continued) The attacker can capture packets as they travel through the network by sniffing The hardware or software that performs such functions is called a sniffer Physical security First line of defense Protects the equipment and infrastructure itself Has one primary goal: to prevent unauthorized users from reaching the equipment or cable plant in order to use, steal, or vandalize it 11

12 Securing Removable Media Securing critical information stored on a file server can be achieved through strong passwords, network security devices, antivirus software, and door locks An employee copying data to a floppy disk or CD and carrying it home poses two risks: Storage media could be lost or stolen, compromising the information A worm or virus could be introduced to the media, potentially damaging the stored information and infecting the network 12

13 Magnetic Media Record information by changing the magnetic direction of particles on a platter Floppy disks were some of the first magnetic media developed The capacity of todays 3 1/2-inch disks are 1.4 MB Hard drives contain several platters stacked in a closed unit, each platter having its own head or apparatus to read and write information Magnetic tape drives record information in a serial fashion 13

14 Optical Media Optical media use a principle for recording information different from magnetic media A high-intensity laser burns a tiny pit into the surface of an optical disc to record a one, but does nothing to record a zero Capacity of optical discs varies by type A Compact Disc-Recordable (CD- R) disc can record up to 650 MB of data Data cannot be changed once recorded 14

15 Optical Media (continued) A Compact Disc-Rewriteable (CD- RW) disc can be used to record data, erase it, and record again A Digital Versatile Disc (DVD) can store much larger amounts of data DVD formats include Digital Versatile Disc-Recordable (DVD-R), which can record once up to 3.95 GB on a single-sided disc and 7.9 GB on a double-sided disc 15

16 Electronic Media Electronic media use flash memory for storage Flash memory is a solid state storage device everything is electronic, with no moving or mechanical parts SmartMedia cards range in capacity The card itself is only 45 mm long, 37 mm wide, and less than 1 mm thick 16

17 Electronic Media (continued) CompactFlash card Consists of a small circuit board with flash memory chips and a dedicated controller chip encased in a shell Come in 33 mm and 55 mm thicknesses USB memory stick is very popular Can hold large amounts of data (+64Gb) 17

18 Keeping Removable Media Secure Protecting removable media involves making sure that antivirus and other security software are installed on all systems that may receive a removable media device, including employee home computers 18

19 Hardening Network Devices Each device that is connected to a network is a potential target of an attack and must be properly protected Network devices to be hardened categorized as: Standard network devices Communication devices Network security devices 19

20 Hardening Standard Network Devices A standard network device is a typical piece of equipment that is found on almost every network, such as a workstation, server, switch, or router This equipment has basic security features that you can use to harden the devices 20

21 Workstations and Servers Workstation: personal computer attached to a network (also called a client) Connected to a LAN and shares resources with other workstations and network equipment Can be used independently of the network and can have their own applications installed Server: computer on a network dedicated to managing and controlling the network 21

22 Switches and Routers Switch Most commonly used in Ethernet LANs Receives a packet from one network device and sends it to the destination device only Limits the collision domain (part of network on which multiple devices may attempt to send packets simultaneously) A switch is used within a single network Routers connect two or more single networks to form a larger network 22

23 Switches and Routers (continued) Switches and routers must also be protected against attacks Switches and routers can be managed using the Simple Network Management Protocol (SNMP), part of the TCP/IP protocol suite Software agents are loaded onto each network device to be managed 23

24 Switches and Routers (continued) Each agent monitors network traffic and stores that information in its management information base (MIB) A computer with SNMP management software (SNMP management station) communicates with software agents on each network device and collects the data stored in the MIBs 24

25 Hardening Communication Devices A second category of network devices are those that communicate over longer distances Include: Modems Remote access servers Telecom/PBX Systems Mobile devices 25

26 Modems Most common communication device Broadband is increasing in popularity and can create network connection speeds of 15 Mbps and higher Two popular broadband technologies: Digital Subscriber Line (DSL) transmits data at 15 Mbps over regular telephone lines Another broadband technology uses the local cable television system 26

27 Modems (continued) A computer connects to a cable modem, which is connected to the coaxial cable that brings cable TV signals to the home Because cable connectivity is shared in a neighborhood, other users can use a sniffer to view traffic Another risk with DSL and cable modem connections is that broadband connections are charged at a set monthly rate, not by the minute of connect time 27

28 Remote Access Servers Set of technologies that allows a remote user to connect to a network through the Internet or a wide area network (WAN) Users run remote access client software and initiate a connection to a Remote Access Server (RAS), which authenticates users and passes service requests to the network 28

29 Remote Access Servers (continued) 29

30 Remote Access Servers (continued) Remote access clients can run almost all network-based applications without modification Possible because remote access technology supports both drive letters and universal naming convention (UNC) names 30

31 Telecom/PBX Systems Term used to describe a Private Branch eXchange The definition of a PBX comes from the words that make up its name: Private Branch eXchange 31

32 Mobile Devices As cellular phones and personal digital assistants (PDAs) have become increasingly popular, they have become the target of attackers Some defenses against attacks on these devices use real-time data encryption and passwords to protect the system so that an intruder cannot beam a virus through a wireless connection 32

33 Hardening Network Security Devices The final category of network devices includes those designed and used strictly to protect the network Include: Firewalls Intrusion-detection systems Network monitoring and diagnostic devices 33

34 Firewalls Typically used to filter packets Designed to prevent malicious packets from entering the network or its computers (sometimes called a packet filter) Typically located outside the network security perimeter as first line of defense Can be software or hardware configurations Software firewall runs as a program on a local computer (sometimes known as a personal firewall) Enterprise firewalls are software firewalls designed to run on a dedicated device and protect a network instead of only one computer One disadvantage is that it is only as strong as the operating system of the computer 34

35 Firewalls (continued) Filter packets in one of two ways: Stateless packet filtering: permits or denies each packet based strictly on the rule base Stateful packet filtering: records state of a connection between an internal computer and an external server; makes decisions based on connection and rule base Can perform content filtering to block access to undesirable Web sites An application layer firewall can defend against worms better than other kinds of firewalls Reassembles and analyzes packet streams instead of examining individual packets 35

36 Intrusion-Detection Systems (IDSs) Devices that establish and maintain network security Active IDS (or reactive IDS) performs a specific function when it senses an attack, such as dropping packets or tracing the attack back to a source Installed on the server or, in some instances, on all computers on the network Passive IDS sends information about what happened, but does not take action 36

37 Intrusion-Detection Systems (IDSs) (continued) Host-based IDS monitors critical operating system files and computers processor activity and memory; scans event logs for signs of suspicious activity Network-based IDS monitors all network traffic instead of only the activity on a computer Typically located just behind the firewall Other IDS systems are based on behavior: Watch network activity and report abnormal behavior Result in many false alarms 37

38 Network Monitoring and Diagnostic Devices SNMP enables network administrators to: Monitor network performance Find and solve network problems Plan for network growth Managed device: Network device that contains an SNMP agent Collects and stores management information and makes it available to SNMP 38

39 Designing Network Topologies Topology: physical layout of the network devices, how they are interconnected, and how they communicate Essential to establishing its security Although network topologies can be modified for security reasons, the network still must reflect the needs of the organization and users 39

40 Security Zones One of the keys to mapping the topology of a network is to separate secure users from outsiders through: Demilitarized Zones (DMZs) Intranets Extranets 40

41 Demilitarized Zones (DMZs) Separate networks that sit outside the secure network perimeter Outside users can access the DMZ, but cannot enter the secure network For extra security, some networks use a DMZ with two firewalls The types of servers that should be located in the DMZ include: Web servers servers Remote access servers FTP servers 41

42 Demilitarized Zones (DMZs) (continued) 42

43 Intranets Networks that use the same protocols as the public Internet, but are only accessible to trusted inside users Disadvantage is that it does not allow remote trusted users access to information 43

44 Extranets Sometimes called a cross between the Internet and an intranet Accessible to users that are not trusted internal users, but trusted external users Not accessible to the general public, but allows vendors and business partners to access a company Web site 44

45 Network Address Translation (NAT) You cannot attack what you do not see is the philosophy behind Network Address Translation (NAT) systems Hides the IP addresses of network devices from attackers Computers are assigned special IP addresses (known as private addresses) These IP addresses are not assigned to any specific user or organization; anyone can use them on their own private internal network Port address translation (PAT) is a variation of NAT Each packet is given the same IP address, but a different TCP port number 45

46 Honeypots Computers located in a DMZ loaded with software and data files that appear to be authentic Intended to trap or trick attackers Two-fold purpose: To direct attackers attention away from real servers on the network To examine techniques used by attackers 46

47 Honeypots (continued) 47

48 Virtual LANs (VLANs) Segment a network with switches to divide the network into a hierarchy Core switches reside at the top of the hierarchy and carry traffic between switches Workgroup switches are connected directly to the devices on the network Core switches must work faster than workgroup switches because core switches must handle the traffic of several workgroup switches 48

49 Virtual LANs (VLANs) (continued) 49

50 Virtual LANs (VLANs) (continued) Segment a network by grouping similar users together Instead of segmenting by user, you can segment a network by separating devices into logical groups (known as creating a VLAN) 50

51 Summary Cable plant: physical infrastructure (wire, connectors, and cables that carry data communication signals between equipment) Removable media used to store information include: Magnetic storage (removable disks, hard drives) Optical storage (CD and DVD) Electronic storage (USB memory sticks, FlashCards) Network devices (workstations, servers, switches, and routers) should all be hardened to repel attackers A networks topology plays a critical role in resisting attackers Hiding the IP address of a network device can help disguise it so that an attacker cannot find it 51


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