SSCP Study Guide and DVD Training System

OSI Model

• There are seven layers in the OSI reference model. The seven layers of the OSI model are the Physical layer, the Data Link layer, the Network layer, the Transport layer, the Session layer, the Presentation layer, and the Application layer.

• A data packet travels down the OSI model from the Application layer down to the Physical layer. The packet then travels across the network to the receiving machine. The packet then travels back up the OSI model on the receiving machine to arrive at the Application layer in the same format that it was sent in.

• The OSI reference model is important to security because as data communications function in a layered model so does network security.

Local Area Networks

• There are five major topologies that LANs: star, bus, tree, ring, and mesh.

• The three access methods are CSMA/CA, CSMA/CD, and token

• Baseband signaling uses digital signals, and broadband signaling uses analog signaling.

• LAN topologies use broadcast technology to send data out across the network.

• Token ring passes a token around to each device on the network. The device that holds the token is permitted to transmit data across the network.

• FDDI is similar to token ring, but uses fiber-optic cables in a much larger environment.

Wide Area Networks

• WANs are networks that span a broad geographic area. The Internet is a WAN.

• Different sites in a WAN are typically connected by a leased line provided by a communication carrier.

• A CSU/DSU is used to terminate the digital signal at the organization's side of a LAN.

• X.25 defines a point-to-point connection between a DTE and DCE.

• A single ISDN line operates at 64 Kbps.

• Frame relay uses existing technologies that can operate at speeds of up to 45 Mbps.

• ATM is a newer technology that can provide speeds of greater than 100 Mbps.

Protocols

• The two categories for protocols are connection-oriented and connectionless.

• IP functions under TCP to create the widely used combination of TCP/IP.

• S/MIME provides a secure method for sending MIME-encoded e-mail messages.

• SSL functions on port 443 and uses a private key to allow for encrypted Internet transmission.

• PAP and CHAP are two common authentication protocols, of which CHAP is the more secure authentication protocol.

• PPP and SLIP are to protocols used to allow remote serial (modem) connections. PPP is the more popular and more widely used protocol.

Network Devices

• Hubs and switches are central points in most networks today. A hub forwards packets to every port while a switch directs packets to specific ports.

• The three topologies for firewalls are packet-filtering, screened-host, and screened-subnet (with DMZ).

• NAT is used to protect an internal network by routing a private IP address to the public using one publicly available IP address.

• A packet-filtering firewall is able to log stealth scans because it monitors the status of all connections, even partially open connection.

• An IDS is used to monitor a network and alert the administrator when it detects an anomaly or attack.

Virtual Private Networks

• A VPN creates a virtual connection between two hosts to securely transmit data.

• PPTP, L2TP, and IPSec are common protocols used to implement VPNs.

• IPSec has two modes: transport mode only encrypts the data portion of a packet, while tunneling mode encrypts the data portion and the header of a packet.

• SSH provides a secure method to create a remote console session with a server.

Typical Attacks Against Network Resources

• Spoofing is the process of impersonating a trusted host to have access to data communications that would not be available to an untrusted device.

• Sniffing involves intercepting data packets in between hosts, known as a MITM attack.

• A SYN flood is a common DoS attack.

• War dialing is the process of randomly dialing phone numbers in order to eventually find a number with a computer on the other end.