Terms 11 Definitions and Questions
TCP/IP • Abbreviation of Transmission Control Protocol, and pronounced as separate letters. TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. • Internet Protocol - The network layer for the TCP/IPprotocol suite widely used on Ethernet networks. IP is a connectionless, best-effortpacket switching protocol. It provides packetrouting, fragmentation and re-assembly throughthe data link layer.
IP Address • An identifier for a computer or device on a TCP/IPnetwork. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 126.96.36.199 could be an IP address. • Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates. • The four numbers in an IP address are used in different ways to identify a particular network and a host on that network.
UDP • (User Datagram Protocol) • A protocol within the TCP/IP protocol suite that is used in place of TCP when a reliable delivery is not required. There is less processing of UDP packets than there is for TCP. • UDP is widely used for streaming audio and video, voice over IP (VoIP) and videoconferencing, because there is no time to retransmit erroneous or dropped packets.
TCP/IP Q/A • Q: What does the address 127.0.0.1 mean? • A: 127.0.0.1 is a loopback network connection. If you telnet, ftp, etc... to it you are connected to your own machine. This is commonly used as a practical joke with people who are new to TCP/IP. It’s also called the “home” address.
127.0.0.1 • Think Geek • http://www.thinkgeek.com/tshirts/coder/5d6a/
Dynamic IP • A term used to describe how IP addresses are dynamically assigned to computers as and when needed. • Unlike Static IP addresses, the IP address is temporary e.g. when you connect to your ISP using a dial-up connection , you PC or router will be dynamically assigned an IP address while you are on-line.
Static IP • Referred to as fixed IP address. • A static IP address is a number that is assigned to a computer by an Internet service provider (ISP) to be its permanent address on the internet.
Dynamic / Static IP Q/A • Q: Who would typically have a static IP address? Why? • A: Large corporations tend to have static IPs for their servers. This allows their clients to consistently access these servers.
DHCP • -Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamicIP addresses to devices on a network. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses. • A method of automatically assigning a TCP/IP address to a client. A DHCP server is used to dole out a TCP/IP address from a pool of TCP/IP addresses to a client that supports DHCP. When you connect to your ISP over a modem or broadband you are typically assigned a dynamic (non-static) TCP/IP address via DHCP. The big advantage to DHCP is that you don't need to manually assign a TCP/IP address to a client--the DHCP server takes care of that. After an amount of time passes where the client does not contact the server, the server puts the TCP/IP address of the client back into the pool to be assigned to that client or any other client hat requests a TCP/IP address. The disadvantage of DHCP for the DHCP client is that the client is not guaranteed to have a particular TCP/IP address at any given time. For that you want a static IP address.
DNS • Domain name servers, or DNS, are an incredibly important but completely hidden part of the Internet. The DNS system forms one of the largest and most active distributed databases on the planet. Without DNS, the Internet would shut down very quickly. • This service maps TCP/IP numbers, such as 188.8.131.52, to a more easily remembered name, such as www.geek.com. Thus, when you type www.geek.com into your browser, it goes out to the DNS server specified by your ISP and asks for a matching TCP/IP address. If the browser finds a DNS entry for the name you typed in, you see the appropriate website. If not, it lets you know. Every domain name that is actually being used for a website has a corresponding TCP/IP address. When you set up a site you have your ISP add a DNS entry to its DNS servers (or manage it yourself). This entry gets replicated across the Internet in a matter of hours, and, once fully replicated, you can reach your website from any Internet connection.
DHCP / DNS Q/A • Q: Does IU use DHCP for dorm connections? • A: Yes. If they didn’t, you would have to call UITS up and request an IP address. Plus, if you took your computer off of the network for a while and they accidentally gave ‘your’ IP address to someone else, you would have an IP conflict if you plugged your machine back in.
Denial of Service • An attack that is specifically designed to prevent the normal functioning of a system, and thereby to prevent lawful access to that system and its data by its authorized users. • On the Internet, a denial of service (DoS) attack is an incident in which a user or organization is deprived of the services of a resource they would normally expect to have. Typically, the loss of service is the inability of a particular network service, such as e-mail, to be available or the temporary loss of all network connectivity and services. In the worst cases, for example, a Web site accessed by millions of people can occasionally be forced to temporarily cease operation. • Although usually intentional and malicious, a denial of service attack can sometimes happen accidentally. A denial of service attack is a type of security breach to a computer system that does not usually result in the theft of information or other security loss. However, these attacks can cost the target person or company a great deal of time and money.
Honey Pot • A honey pot is a computer system on the Internet that is expressly set up to attract and "trap" people who attempt to penetrate other people's computer systems. To set up a honey pot, it is recommended that you: • Install the operating system without patches installed and using typical defaults and options • Make sure that there is no data on the system that cannot safely be destroyed • Add an application that is designed to record the activities of the invader • Maintaining a honey pot is said to require a considerable amount of attention and may offer as its highest value nothing more than a learning experience (that is, you may not catch any crackers).
War Dialing • A war dialer is a computer program used to identify the phone numbers that can successfully make a connection with a computer modem. The program automatically dials a defined range of phone numbers and logs and enters in a database those numbers that successfully connect to the modem. Some programs can also identify the particular operating system running in the computer and may also conduct automated penetration testing. In such cases, the war dialer runs through a predetermined list of common user names and passwords in an attempt to gain access to the system. • An identical technique was sometimes used to get the first call for prizes in radio "call-in" shows, thus leading to the adoption of random "fifth caller," "secenteenth caller" etc. by radio stations to circumvent this practice.
WiFi • Short for ‘wireless fidelity’. A term for certain types of wireless local area networks (WLAN) that use specifications conforming to IEEE 802.11. • WiFi has gained acceptance in many environments as an alternative to a wired LAN. Many airports, hotels, and other services offer public access to WiFi networks so people can log onto the Internet and receive emails on the move. • These locations are known as hotspots.
War Chalking • Warchalking is the practice of marking a series of symbols on sidewalks and walls to indicate nearby wireless access. That way, other computer users can pop open their laptops and connect to the Internet wirelessly. • As the Warchalking web site states, this kind of language was first utilized by hobos during the Great Depression to communicate with each other for various purposes, mostly to find safe harbor. Warchalking itself capitalizes on this idea. Wireless users help other wireless users by communicating about nearby access points • Creator Matt Jones began by posting three possible war chalking symbols on his blog. Two semi-circles back-to-back would indicate an open node, a circle would indicate the presence of a closed node, and a circle with the letter "W" inside it would indicate a WEP node. Ideally, each symbol would be chalked with a corresponding SSID next to it which would act as a password to the node.
War Driving • A computer cracking technique that involves driving through a neighborhood with a wireless-enabled notebook computer and mapping houses and businesses that have wireless access points.
War Q/A • Q: Other than people trying to break into computers, who might use a wardialer or wardialer-like system? • A: Telemarketers use wardialer-like systems to call hundreds of numbers at once, and then transfer numbers that picked up to salesmen. In this case, they’re actually looking for numbers –not- connected to modems or faxes.
Short Quiz • Please get out a blank sheet of paper and put your name and the date on it.
Short Quiz • Define “HTML”. • Define “DRM”. • Analog signals are composed of discrete 1s and 0s – T/F? • Your intranet and extranet are often separated by a _______ designed to keep out intruders. • How many signals are needed for GPS to precisely pinpoint your location?
Short Quiz • Hyper Text Markup Language • Digital Rights Management • F • Firewall • 3