PSAD is a tool that runs on the Windows OS and analyzes iptables log messages to detect port scans and other suspicious traffic. It includes many signatures from the IDS to detect probes for various backdoor programs such as EvilFTP, GirlFriend, SubSeven, DDoS tools (mstream, shaft), and advanced port scans (FIN, NULL, XMAS). If it is combined with fwsnort and the Netfilter string match extension, it detects most of the attacks described in the Snort rule set that involve application layer data.
Answer option C is incorrect. NetRanger is the complete network configuration and information toolkit that includes the following tools: Ping tool, Trace Route tool, Host Lookup tool, Internet time synchronizer, Whois tool, Finger Unix hosts tool, Host and port scanning tool, check multiple POP3 mail accounts tool, manage dialup connections tool, Quote of the day tool, and monitor Network Settings tool. These tools are integrated in order to use an application interface with full online help. NetRanger is designed for both new and experienced users. This tool is used to help diagnose network problems and to get information about users, hosts, and networks on the Internet or on a user computer network. NetRanger uses multi-threaded and multi-connection technologies in order to be very fast and efficient.
Answer option D is incorrect. Nmap is a free open-source utility for network exploration and security auditing. It is used to discover computers and services on a computer network, thus creating a "map" of the network. Just like many simple port scanners, Nmap is capable of discovering passive services. In addition, Nmap may be able to determine various details about the remote computers. These include operating system, device type, uptime, software product used to run a service, exact version number of that product, presence of some firewall techniques and, on a local area network, even vendor of the remote network card. Nmap runs on Linux, Microsoft Windows, etc.

Internet Protocol Security (IPSec) is a standard-based protocol that provides the highest level of VPN security. IPSec can encrypt virtually everything above the networking layer. It is used for VPN connections that use the L2TP protocol. It secures both data and password. IPSec cannot be used with Point-to-Point Tunneling Protocol (PPTP). Answer option B is incorrect. The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched inter-network using the Internet Protocol Suite, also referred to as TCP/IP. IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering distinguished protocol datagrams (packets) from the source host to the destination host solely based on their addresses. For this purpose, the Internet Protocol defines addressing methods and structures for datagram encapsulation. The first major version of addressing structure, now referred to as Internet Protocol Version 4 (IPv4), is still the dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6), is being deployed actively worldwide. Answer option C is incorrect. Point-to-Point Protocol (PPP) is a remote access protocol commonly used to connect to the Internet. It supports compression and encryption and can be used to connect to a variety of networks. It can connect to a network running on the IPX, TCP/IP, or NetBEUI protocol. It supports multi-protocol and dynamic IP assignments. It is the default protocol for the Microsoft Dial-Up adapter. Answer option D is incorrect. Layer 2 Tunneling Protocol (L2TP) is a more secure version of Point-to-Point Tunneling Protocol (PPTP). It provides tunneling, address assignment, and authentication. It allows the transfer of Point-to-Point Protocol (PPP) traffic between different networks. L2TP combines with IPSec to provide tunneling and security for Internet Protocol (IP), Internetwork Packet Exchange (IPX), and other protocol packets across IP networks.

Token Ring
Explanation:
A Token Ring network is a local area network (LAN) in which all computers are connected in a ring or star topology and a bit- or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. The Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet. The IBM Token Ring protocol led to a standard version, specified as IEEE 802.5. Both protocols are used and are very similar. The IEEE 802.5 Token Ring technology provides for data transfer rates of either 4 or 16 megabits per second. Working: Empty information frames are constantly circulated on the ring. When a computer has a message to send, it adds a token to an empty frame and adds a message and a destination identifier to the frame. The frame is then observed by each successive workstation. If the workstation sees that it is the destination for the message, it copies the message from the frame and modifies the token back to 0.When the frame gets back to the originator, it sees that the token has been modified to 0 and that the message has been copied and received. It removes the message from the particular frame.The frame continues to circulate as an empty frame, ready to be taken by a workstation when it has a message to send.