PC Security Introduction

What level of encryption should you use when encrypting wireless?

128 bit or higher. Yes, 128-bit is the minimum encryption level you should be using.

What is the current wireless band frequency?

2.4 GHz to 5 GHz. The 802.11 wireless networks work on a frequency between 2.4 and 5 GHz.

Data-Link Protocl

802.3, ARP, WAP, PPP What It Is: Delivers & receives data from the Physical Layer Example: Converts 1s and 0s to packets to send up or prepares the packets to be sent and converts the incoming data to packets to send up to the Network Layer

Buffer Overflow

A buffer overflow is a great example of this difference. A buffer in computers is a temporary storage space for data until the user or the device programming places it somewhere else. An overflow occurs when the amount of data stored in the buffer exceeds the amount it can handle.

Cable

A connection that uses the cable lines commonly used for cable television access to connect to the Internet

What is virtual memory?

A creation of the computer. Virtual memory is the creation of the computer. For instance, like a Window's swap file where memory is set aside to manage tasks. The memory disappears when the computer is shut down.

Firewall

A firewall can be a software program installed on a single computer or a piece of hardware standing between the inside of a network and the outside world. Firewalls enable you to block these hackers with a reasonable amount of success while still allowing you to access the Internet. (You'll learn more about these in a future lesson!)

What is a Gateway device?

A multi-function device usually found with bundled services or wireless.

Network

A network is a series of one or more computers or devices (such as printers) connected to each other.

What causes an exploit?

A person or program takes advantage of a known vulnerability. An exploit is a program or technique that takes advantage of a vulnerability.

Dial-Up

A phone line connection between the modem on your PC and the Internet service provider. While not used any longer, this connection type will be useful as a reference to help you understand bandwidth.

How are VPNs created?

A process called tunneling. VPNs are created through the process of tunneling which wraps data into a packet and send the wrapped packet through another packet across a network.

Remote Access VPN

A remote access VPN is a user-to-LAN connection used by a company or individuals that has members who need to connect to the private network from various remote locations. You use a remote access VPN if you use a VPN to surf anonymously. NordVPN, TunnelBear, Golden Frog and Hide My Ass are some of the more common ones.

Authentication

A server is considered secure when it is configured to require the user or client to authenticate itself. Meaning, the server wants you to verify that you are who you say you are. This is called authentication. When a user accesses a secure server, the authentication process takes place by password. If data is accessing a server, the process uses encryption.

T1

A special trunk (T) line run to your location that has a higher speed available than copper phone wires have for transmitting data because there are several lines bundled to create the trunk.

What is a breach?

A state when something has entered a network or network device without the necessary permission to do so. Also called a compromise, this is the condition where your security and safety are questionable causing a breach.

What is asymmetric encryption?

A two key encryption system. Also called public-key encryption, asymmetric encryption requires two keys. One key encrypts data, the other is used to decrypt the data.

Client

After data is transmitted, how does one computer know that the data sent is safe for it to receive it? There is a variety of ways that PCs communicate, but the most common method used is to require a login or some sort of verification that the data is sent from a reliable source. When a network requires a user to log in, there is a variety of code that transfers between computers. If you are logging into a server, your machine is called the client.

IP4 VS IP6

An IPv6 address has 8 "hextets" rather than 4 octets.

What is the Wi-Fi Alliance?

An association formed to certify interoperability of wireless Local Area Network products based on the IEEE 802.11 specification. The Wi-Fi Alliance is a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specifications.

What is a socket

An endpoint. A socket in networking is an endpoint in communication between two devices. It can be an IP address or a port.

Exploit

An exploit is a program or technique that hackers can use to take advantage of a vulnerability in software, break security, or otherwise attack a PC over the network. (Source: Symantec.com) In the English language, exploit means to take advantage of a person or situation. In computing, this is exactly what an exploit accomplishes. It takes advantage of a vulnerability. Within hours of an announcement that a new vulnerability is discovered, there is an exploit. This is the main reason we have repeated the need to keep up-to-date with security notices for your operating system and software! You may be wondering why anyone would need or want remote access to your PC. The truth is there are many reasons why a person may want remote access to your PC including: using the PC for an attack on another computer or Web server, accessing confidential data, tying up a network's resources, sending spam, launching a new worm, virus, or other malicious code, and more! In large company networks, they want access to gather business intelligence—also known as spying.

Intranet VPN

An intranet-based VPN is used to connect one or more remote locations that you wish to join in a single private network. You create an intranet VPN to connect LAN to LAN. This is a VPN that is already set up by a company you work for. They have their own VPN that you likely connect to by signing in to the company network. Typically, it contains information about employee benefits, company news the staff may find of value and even staff directories for convenience.

UPnP

Another universal vulnerability is found in Microsoft's Universal Plug and Play (UPnP). Plug and Play (PnP) is the standard developed for creating hardware, not an installation wizard nor any software related to it. UPnP is different from the Plug and Play standard. You learned how IP communicates with another computer over the OSI model. What UPnP does is open the channel in the OSI model and send out a message to any computer within listening range announcing it is an Internet server. It uses the User Datagram Protocol (UDP) packet through Port 1900.

Unlike hardware firewalls, the software firewall operates on what layer of the OSI model?

Application Layer. Because it is software based, it operates on the layer closest to the applications and the user.

LAN

At home or in a small office, you may have a LAN, or local area network. The difference between a WAN and LAN is distance between all the connections. LANs are usually within the same building, a campus or close proximity of other offices.

Where is the best place to stop an unwanted connection?

At the packet using a router with a firewall. If you stop the packet there is not communication and therefore no connection is established. This can only be accomplished with a router using a built-in firewall.

Why is the OSI model important to networks?

Because it guarantees communication. Regardless of the operating system, PC manufacturer or software you use, the OSI model guarantees you will always be able to communicate across a network

Boot Sector Viruses

Boot sector viruses infect the system area of a disk—that is, the area of floppy disks, hard disks, or bootable USB drives that tells the computer how to start the PC or the floppy. All floppy disks and hard disks (including disks containing only data) contain a small program in this area that runs when the computer starts up. On USB drives, the boot sector virus can hide in the autorun.inf file. Boot sector viruses attach themselves to this part of the disk and activate when the user attempts to start up from the infected disk. These viruses are always memory resident in nature. Most were written for DOS, but all PCs, regardless of the operating system, are potential targets of this type of virus. All that is required to become infected is to attempt to start up your computer with an infected floppy disk. After that, while the virus remains in memory, all floppy disks that are not locked from further writing, or write protected, will become infected when the floppy disk is accessed. Examples of boot sector viruses are Form, Disk Killer, Michelangelo, and Stoned. On bootable USB drives, an autorun virus can infect the entire hard drive boot sector. Your antivirus software protects your main hard drive boot sector from being infected by any newer boot sector viruses. Two of the more common USB viruses are: Worm:inf/Autorun.gen!A and Worm:Inf/Hamweg.gen!A.

Which protocol enables an ISP to assign a dynamic IP address?

DHCP. Dynamic Host Configuration Protocol or DHCP enables ISPs to dynamically change an IP address when it needs to.

Frames

Data travels across network connections in a variety of ways. Some networks use frames, which are units of data exchanged within a network or subnetwork.

How do you put ports in stealth mode?

Disable the ping (ICMP echo) packet, remote administration and UPnP in your router or gateway... Yes, by disabling the response to pings from the Internet in your router or gateway, your ports will appear stealth because they will not respond. Both remote administration and UPnP have the same effect as a ping (ICMP echo) packet.

What files on a computer are used as translators for hardware to speak to software?

Drivers. Driver files are the translators used by the computer to interpret commands from programming code.

Encoding

Encoding is a process where the actual virus text is masked by converting the programming code to a different character set like base-64. The virus tells the machine that it's base-64 encoding and then has a script to decode the characters to a machine readable format. In the past, this type of malware could hide from the AV software. Now, most include a signature for anything with the words base64 in the text and the file is quarantined immediately.

Encryption

Encryption is the process of changing data into a disguised format so your information is kept private. There are programs that provide the encryption, and many of the new protocols have the encryption built into the programming code. Many networks will use encryption and authentication together. IPSec, or IP Security, is a whole package of authentication and encryption protocol for all types of network traffic on Internet protocol. This is the protocol you use to create a Virtual Private Network (VPN). Why would you want to keep your networks secure by encrypting data or authenticating passwords? Because you want to keep out hackers or crackers.

What's the difference between wired and wireless routers?

Encryption. Because a wired device does not flow through the airwaves it does not need protection. Wireless signals however, can be intercepted and therefore requires encryption to travel securely. Wireless routers provide encryption.

Ethernet

Ethernet networks are the hard-wired types of connections.

Exposure

Exposure, on the other hand, is a state in which a computer system (or set of systems) that does not have a known universal vulnerability is still capable of allowing the following: An attacker to conduct information gathering activities. An attacker to hide activities. A capability that behaves as expected but can be easily compromised or, in other words, has a major weakness or flaw in it Is a primary point of entry that an attacker may attempt to use to gain access to the system or data. Is considered a problem according to some reasonable security policy. Exposure and vulnerability look a lot alike in definition, don't they? Then what is the difference? Well, the best way to illustrate the difference is to look at an example. Example An example of exposure is using an instant messaging service. There exists within the messaging service the potential to gain access to the entire filing system of the computer system. That potential is a threat if you use an instant messaging service with the PC security relaxed by allowing file sharing of the entire computer. Therefore, if you use the instant messaging service, you are exposed to the potential risk, but you are not vulnerable unless you open up your entire PC to file sharing.

FiOS/FIOS

Fiber Optic connections use strands of glass the size of a piece of human hair that sends signals through light waves generated by a laser.

File Infector Viruses

File infector viruses infect program files. These viruses normally infect executable code, such as .com and .exe files. They can infect other files when an infected program is run from floppy, hard drive, or from the network. Many of these viruses are memory resident, meaning they stay active in the background of the computer and come back on a new boot of your PC. After it stays running in the background memory, any noninfected program or program file that runs becomes infected. Examples of known file infector viruses include Jerusalem and Cascade.

The top three weaknesses in operating systems are?

Flaws in RPC protocol programming code. Security holes in standard protocols. Unintended access and privilege to the core.

GRE

GRE is not a protocol. In fact, GRE stands for Generic Routing Encapsulation, which is a method of packaging the packet for transporting across the Internet. If GRE is used, you still need a protocol to transport the encapsulated packet.

HMAC

HMAC authentication requires that each packet is signed with a hash or hash function to verify that the source is legitimate. The H in the acronym represents the term hash. The remaining letters—MAC—represent, message authentication code.

Network

ICMP, IP, IGMP, IPv4, IPv6, IPSec, NAT, GRE, RIP What It Is: Responsible for routing traffic across the network. Example: Packets, Routing, Addressing

Octet

IP addresses are expressed in the octet format like this: 127.27.11.100.

Physical Protocol

IP, IPX, 802.3 What It Is: Loosely, the physical structure of the network. Example: Ethernet cards, hubs, routers, the network design as a whole.

Which is considered the most secure protocol available today?

IPSec. IPSec, the protocol used for encapsulating VPN data is considered the most secure protocol today.

Router

If you have more than one computer connected to the Internet, you will use a router to allow all the computers on the network to share the connection. Routers communicate to the computers through packets. Packets are units of data exchanged between computers or routers.

What is the difference between a vulnerability and exposure?

In exposure, the possibility for a vulnerability exists but it does not have a universal vulnerability present. Exposure is a state where a computer system or network does not have a known universal vulnerability but still has the potential to comprise security.

ISO/OSI

International Organization for Standardization/Open system interconnect

ICMP

Internet Control Message Protocol

L2F

Layer Two Forwarding (L2F) protocol is a tunneling protocol developed by Cisco Systems. It's similar to the PPTP protocol developed by Microsoft. It enables organizations to set up VPNs that use the Internet to move packets.

Presentation Protocol

MIME, Telenet, XDR What It Is: Formats the data from the Programs or Apps into data the device can use. Example:Sending a large graphic that needs to be compressed. Sending a file to someone on a different OS.

Master Boot Record Virus

Master boot record viruses are memory resident viruses that infect disks in the same manner as boot sector viruses. The difference is where the viral code is located. Master boot record viruses normally save a legitimate copy of the master boot record in a different location where the operating system cannot find it. Examples of master boot record viruses are NYB, AntiExe, and Unashamed.

PPTP (Point-to-Point Tunneling Protocol)

Microsoft and several other companies developed PPTP, short for Point-to-Point Tunneling Protocol for VPNs. With PPTP, users can dial in to their corporate network via the Internet.

Multi-partite Virus

Multi-partite (also known as polypartite) viruses infect both the area where the computer stores information on how to start the computer (boot area), and program files (executables, dlls, and so forth). These are particularly difficult to repair. If the boot area is cleaned but the files are not, the boot area will be reinfected. The same holds true for cleaning infected files. If the virus is not removed from the boot area, any files that you have cleaned will be reinfected. Examples of multi-partite viruses include One_Half, Emperor, Anthrax and Tequilla. Macro viruses

Protocol

Networks are based on the method in which they communicate, also called the protocol. Most networks today communicate through IP or TCP/IP protocols. A protocol is nothing more than programming code created to allow communication.

WordPress Vulnerability

One of the simpler vulnerabilities to explain is a hole in a script used on many web sites—WordPress—which is built on the PHP programming language. While WordPress was developed with the help of a lot of programmers, it's not infallible in terms of security. The most common vulnerability found repeatedly in WordPress sites is something called XSS or Cross-Site Scripting. In Cross-Site Scripting, the program code is tricked to accept data it normally would reject. Which means a malicious hacker could inject any malicious code into a website and cause serious damage.

What port does the Universal Plug and Play vulnerability open to the Internet?

Port 1900. The Universal Plug and Play vulnerability opens Port 1900 and announces to any computer listening that your PC is an Internet server.

POP

Post Office Protocol

Integrated services digital network (ISDN) and digital subscriber line (DSL)

Private connections made through a pair of copper wires normally used for phone service. ISDN and DSL is now being offered through FiOS when the fiber cables are part of a node and then portioned off to individual subscribers. This differs from the actual fiber optic cable coming directly to the subscribers' home or office.

Session Protocol

RPC, SQL, NFS. TCP/IP What It Is: Establishes a session, security, logging and such for the purposes of exchanging data. Example: Attempting to establish a connection to a server or other device.

L2TP (Layer 2 Tunneling Protocol)

Recently, Microsoft and Cisco agreed to merge their respective protocols into a single, standard protocol called Layer Two Tunneling Protocol (L2TP).

SYN-ACK (synchronization-acknowledgment)

Remember that a SYN packet is a request to see if you're there. An ACK packet confirms that you are. Port scans do just that.

What are the three types of VPNs?

Remote access, intranet-based, and extranet-based. Remote access is a user-to-LAN VPN connection, intranet-based is VPN used to connect remote users to a private network, and extranet-based is a LAN-to-LAN connection.

RIP

Routing Information Protocol (RIP).

Application Protocol

SMTP, IMAP, DHCP, DNS, HTTP, HTTPS, FTP, POP, TLS/SSL What It Is: The Programs or Apps that allow you to interact with your device. Example: Email program, Word Processing, File Sharing.

SMTP

Simple Mail Transfer Protocol.

Sonnet or other banded bandwidth

Sonnet is the SBC (ATT) name for banded (joined) bandwidth. Many other companies offer the same service under various trade names. These lines are usually combinations of various trunk lines based on the amount of speed you request. For example, Sonnet is usually three T1s joined into a single access point for high-speed access when there are many users. Universities and very large corporations typically use this type of bandwidth. Don't confuse this ATT service with the consumer U-Verse service. This is a corporate service only.

What is open source

Source code that is openly available and freely distributed to everyone without charge. This code is also distributed under the GNU General Public License.

TCP/IP

TCP protocol is an acronym for transmission control protocol, while the IP portion is still Internet protocol. When you put them both together, it's called TCP/IP. This refers to the entire suite of programming codes that allow communications across networks and the Internet.

Transport Protocol

TCP, SPX, UDP What It Is: Responsible for transporting data to the network layer or up to the session layer. Example: Breaks up large packets to a smaller size, attaches addresses if necessary and provide connection services

Required Tunneling Protocols

The Carrier protocol is used by the network that the information is traveling through. If it's traveling across the Internet, for example, it uses the IP protocol. This is because the Internet uses the IP protocol... The Encapsulating protocol is what is wrapped around the original data. Some examples are GRE, IPSec, L2F, PPTP, and L2TP. These protocols will be explained in more detail shortly.

IEEE & WI-FI Allance

The IEEE sets the standards, and the Wi-Fi Alliance certifies that devices and software meet the standards.

Who sets the standards on wireless?

The Institute of Electrical and Electronics Engineers (IEEE). The IEEE or Institute of Electrical and Electronics Engineers is the group that sets the wireless standards.

For a router with a built-in firewall, where do you find the setting to block ping requests?

The Tools, Filtering, security, or advanced tab. Depending on the manufacturer, you will find ping blocking in the Tools, Filtering, security or advanced tab.

IP

The acronym IP stands for Internet protocol and was developed by UNIX. This method allows communication across the Internet and across all operating systems (also called platforms). This is why Macs can see the same information as a Windows machine and communicate as if they were all on the same system.

802.11n

The concept of 802.11n is to create a faster wireless. It was never supposed to enhance security. There were hopes, however, that while they were drafting the new standard, a new security implementation could be drafted too. We are not seeing it.

What makes a VPN different from a conventional network?

The conventional network is always visible where the VPN only becomes real when it's connected to. You do not share VPN connections openly as you do conventional network connections. A VPN only becomes a reality when a connection is made.

Presentation Layer

The presentation layer formats the data to be presented to the application layer. This means it translates data from a format used by the application into a common format for sending and receiving. Data compression, encryption and decryption all take place here. This is also where your data is converted into 0s and 1s. Graphic Interchange Format (GIF) and Joint Photographic Experts Group (JPEG) graphic formats work in this layer.

Excluding the OSI model, hardware, and programming code, what is the weakest link in software?

The responsible party for keeping software updated. Aside from the vulnerabilities in programming code for software and its interaction with the Application Layer of the OSI model, the responsible party for keeping software updated is the weakest link in software applications.

xData or Fractional T1

The same line as described above for the T1, except that a full trunk line is cut into sections depending upon the speed you request.

Macro Viruses

These types of viruses infect data files. They are the most common and have cost corporations the most money and time trying to repair When Microsoft introduced Visual Basic in Microsoft's Office 97, a macro virus could be written that not only infects data files, but would also infect other files as well. Macro viruses infected Microsoft Office Word, Excel, PowerPoint, and Access files. Since Microsoft has changed the way macros are handled in all the newer versions of Office, the macro virus is almost extinct.

Application Layer

This layer is not what you may think the name implies. While applications (software programs) do work on this layer, the protocol that supports the application does also. Therefore, if you are sending or receiving e-mail, your e-mail software is not only working on this layer, but the Simple Mail Transfer Protocol (SMTP) is too.

Session Layer

This layer manages communication sessions and terminates them. In all communications across a network, one computer initiates a session by requesting a response from another. When the receiving computer answers the response, the session starts and communication begins. A computer, a router, a software application, and any other device on a network can initiate the communication. The protocols used at this layer are Secure Socket Layer (SSL) and Remote Procedure Call (RPC).

Wild

This measures how far a virus is already spreading among computer users. This measurement includes the number of infected independent sites and computers, the geographic distribution of infection, the ability of current technology to combat the threat, and the complexity of the virus.

Distribution

This measures how quickly the threat can spread. This measurement includes triggered events, clogging e-mail servers, deleting or modifying files, releasing confidential information, performance degradation, errors in the virus code, compromising security settings, and how quickly the damage may be fixed.

Polymorphic Viruses

This virus infects files with an encrypted copy of itself, which is decoded by a decryption module. However, this decryption module is also modified by each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures.

Metamorphic Viruses

To avoid detection, these viruses rewrite themselves completely each time they infect new executables.

What is the best method for protecting the perimeter?

Use a software or hardware firewall. The best defense is using a software or hardware firewall to stop activity at the point of contact to untrusted services.

Satellite

Used in areas where a standard Internet connection is not possible or impractical. Also considered a broadband connection, this is a type of connection that uses satellites in our atmosphere to send and receive data to and from the Internet to the subscriber.

Microwave

Used in primarily rural areas both in the United States and other countries, the Internet access is connected to a main receiving location and then is broadcast to subscribers in the surrounding area through a tower and microwave dish. This may also appear as a wireless connection depending upon where and how the microwave in the community is configured.

UDP

User Datagram Protocol

What are the types of wireless encryption?

WEP, WPA and WPA2. These are the types of encryption available in wireless routers. WPA2 is the recommended method since WEP and WPA are easily hacked

802.11ac

We are now at 802.11ac. It is faster and more scalable than 802.11(n). And while MIMO appeared with (n), ac brings with it MU-MIMO which allows better control with up to 4 devices communicating all simultaneously without interference. 802.11ac is also 6 times faster than the (n) standard. This makes it a much better option for streaming and gaming devices sharing the same WiFi network. And remember the device interference mentioned above? Wireless-AC focuses its power by running on the 5 GHz frequency band which rises above the clutter of all the other older devices.

When is a raw socket dangerous in an operating system?

When it allows unsecured access to the root or core of the network. Under normal circumstances, the raw socket is protected to allow only administrators who have root privileges. An operating system that grants unrestricted access to this core is dangerous.

ISP

When you connect to the Internet, either from work or home, you use an Internet service provider, also called an ISP. Your ISP may be invisible. That is, at work you have a connection that is always on and requires no logging in on your part. You click your browser and go surfing for what you need. At home, however, your ISP is either DSL, or any broadband provider such as Cable Modem, Fiber Optics, open wireless (Wi-Fi), satellite or microwave. In the beginning of the Internet, dial-up connections used your internal or external modem to dial into the provider's server. From there, you would access the Internet. With DSL, other broadband, or wireless your Internet connection is slightly different.

WAN

When you log into the Internet, you are accessing a type of wide area network, also called a WAN. However, the Internet is not the only WAN. A large business that has offices spread across the United States might have servers in Atlanta and Chicago, yet users in New York and Canada have access to them. This is also a WAN.

WPA

Wi-Fi Protected Access (WPA) is the 2003 replacement for WEP.

WPA2

Wi-Fi Protected Access 2 (WPA2) is the current standard since 2008. There are several versions of this standard, and it's required on all wireless devices bearing the Wi-Fi trademark. WPA2-PSK (Pre-Shared Key) and WPA2-ENT (Enterprise) modes are the different versions available. The Supplementary Materials section for this lesson has a link to more information for understanding these different protocols from Cisco.

WEP

Wired Equivalent Privacy (WEP) is the original protocol used when the wireless standard was ratified in September 1999. Since then, multiple flaws in the security have been detected, making WEP very unsecure to use.

802.11g

Wireless (g) has a transfer speed of 54 Mbps and (n) is capable of 600-900 Mbps. That's 10 times the transfer speed! Wireless (n) also opened the way for MIMO—multiple-input multiple-output. This is what allows you to connect multiple devices to the same WiFi connection without sacrificing speed or data transfer.

WI-FI

Wireless Fidelity

Wireless

Wireless access may be provided directly from any of the ISPs described above, but you have a modem or router that sends the signal to all your wireless devices. You may also live in a smart city where there is open WiFi freely available.

Full-duplex/Half-duplex

You can also transmit data in full-duplex and half-duplex modes. Full-duplex is where both sender and receiver can send information at the same time. Half-duplex communications can only go in one direction at a time. Which method your network uses depends on your Ethernet or network interface card (NIC).

IPSec

You know that IP is Internet protocol and that it is used to transmit information across the Internet. You also learned IPSec is IP Security protocol used for VPNs.

Extranet VPN

You use an extranet-based VPN connection when you have a close relationship with another company (for example, a partner, supplier, or customer). You can build an extranet VPN that connects LAN to LAN, and that allows all of the various companies or users to work in a shared environment. This is a VPN that is set up by your company that allows you to access the private network remotely. Typically, it contains more business-critical information including internal systems and files such as sales presentations or product lists.

Network Layer

layer defines the network address as well as manages routing and forwarding of data. This is where IP is used. Two other protocols used at this level are the Internet Control Message Protocol (ICMP) and Routing Information Protocol (RIP). ICMP is an Internet protocol that allows routers to inform other routers of routing problems. It is also capable of suggesting better routes for data to travel. This is also the protocol used when you ping or trace a network route. RIP is also an IP that directs data traffic. However, RIP uses hop counts to rate traffic. You will see an example of hop counts when you complete your assignment. In networking, the hop count represents the total number of devices a given piece of data (packet) passes through. The more hops data must traverse to reach their destination, the greater the transmission delay incurred. This layer is where all the IPs are working, which is contained in the operating system of your PC.

Data-Link Layer

layer is the portion of the system that provides the synchronization of data traveling across the physical layer. Included in this layer is the error control and flow control for modem operations, the Ethernet transfer of data, and some layers of protocol for communications. This is the level of electronic communication within your PC and your networking hardware where the drivers and the software control communications and transfer of data across the network connection.

Transport Layer

layer manages the flow of data from one end of the traffic to the other. This ensures data is flowing smoothly across the network and does not lose any of the information it is sending. TCP and User Datagram Protocol (UDP) are parts of this layer. This is where the message segmentation and acknowledgement takes place as well as traffic control. Here, the protocol and electrical components of your PC do all the work.

Physical Layer

layer of a network is the electrical and mechanical functions for establishing and maintaining the actual communication of a network. Within the physical layer are specifications for defining voltage levels, physical data transfer rates, and connectors. It may be easy for you to identify the physical layer of a network as the hardware portion of it. This would be the PC itself, motherboard, Ethernet card, or modem.

PKE

public key encryption