The purpose of an OSI reference is to guide vendors and developers so the digital communication products and software programs can interoperate. Following are the OSI layers:. Physical Layer: Responsible for transmission of digital data from sender to receiver through the communication media,. Data Link Layer: Handles the movement of data to and from the physical link.
It is also responsible for encoding and decoding of data bits.
Network Layer: Responsible for packet forwarding and providing routing paths for network communication. Session Layer: Controls connection between the sender and the receiver. It is responsible for starting, ending, and managing the session and establishing, maintaining and synchronizing interaction between the sender and the receiver. Application Layer: It provides an interface between the application and the network. It focuses on process-to-process communication and provides a communication interface.
It is used to create a safe and encrypted connection. When you use a VPN, the data from the client is sent to a point in the VPN where it is encrypted and then sent through the internet to another point. At this point, the data is decrypted and sent to the server. When the server sends a response, the response is sent to a point in the VPN where it is encrypted and this encrypted data is sent to another point in the VPN where it is decrypted. And finally, the decrypted data is sent to the client. The whole point of using a VPN is to ensure encrypted data transfer.
Threat : Someone with the potential to harm a system or an organization Vulnerability : Weakness in a system that can be exploited by a potential hacker Risk : Potential for loss or damage when threat exploits a vulnerability. They can write malware which can be used to gain access to these systems. This type of hackers misuse their skills to steal information or use the hacked system for malicious purpose. These are mostly hired by companies as a security specialist that attempts to find and fix vulnerabilities and security holes in the systems.
They use their skills to help make the security better.
If they find any vulnerabilities, they report it to the owner. Unlike Black hat hackers, they do not exploit the vulnerabilities found. Patch management should be done as soon as it is released.
One would expect a text such as this to be neutral, but it is not. This authoritative Guide to Computer Network Security explores computer network infrastructures and protocol design security flaws, and discusses current security solutions and best practices in both fixed and mobile computer networks. Let us now consider how viruses are transmitted. When Computers first began to be society at large, the absence of ethical standards about their use and caused some problems. Later, we will discuss the software components consisting of the transmission control system. Although the book has been in production since , when it was selected as a Choice Outstanding Academic Title, the core theme of the book has endured. But as long as the technology was still in the hands of the privileged few, incidents of outsider system penetration were few.
For windows, once the patch is released it should be applied to all machines, not later than one month. Same goes for network devices, patch it as soon as it is released. Proper patch management should be followed. Since BIOS is a pre-boot system it has its own storage mechanism for settings and preferences.
A simple way to reset is by popping out the CMOS battery so that the memory storing the settings lose its power supply and as a result, it will lose its setting. Then the hacker joins this communication. The data from both the parties are sent to the hacker and the hacker redirects the data to the destination party after stealing the data required. While the two parties think that they are communicating with each other, in reality, they are communicating with the hacker.
DDOS attack can be classified into two types:. XSS can be used to hijack sessions and steal cookies, modify DOM, remote code execution, crash the server etc. Address Resolution Protocol ARP is a protocol for mapping an Internet Protocol address IP address to a physical machine address that is recognized in the local network. When an incoming packet destined for a host machine on a particular local area network arrives at a gateway, the gateway asks the ARP program to find a physical host or MAC address that matches the IP address.
The ARP program looks in the ARP cache and, if it finds the address, provides it so that the packet can be converted to the right packet length and format and sent to the machine. If no entry is found for the IP address, ARP broadcasts a request packet in a special format to all the machines on the LAN to see if one machine knows that it has that IP address associated with it. Restricting the users from accessing a set of services within the local area network is called port blocking.
Stopping the source to not to access the destination node via ports. As the application works on the ports, so ports are blocked to restricts the access filling up the security holes in the network infrastructure.
A Botnet is a number of devices connected to the internet where each device has one or more bots running on it. The bots on the devices and malicious scripts used to hack a victim. Botnets can be used to steal data, send spams and execute a DDOS attack. Salt is a random data.
When a properly protected password system receives a new password, it creates a hash value of that password, a random salt value, and then the combined value is stored in its database. This helps to defend against dictionary attacks and known hash attacks. Example: If someone uses the same password on two different systems and they are being used using the same hashing algorithm, the hash value would be same, however, if even one of the system uses salt with the hashes, the value will be different.
SSL can help you track the person you are talking to but that can also be tricked at times. Requires not only a password and username but also something that only, and only, that user has on them, i. Authenticator apps replace the need to obtain a verification code via text, voice call or email.
Cognitive Cybersecurity is an application of AI technologies patterned on human thought processes to detect threats and protect physical and digital systems. Self-learning security systems use data mining, pattern recognition, and natural language processing to simulate the human brain, albeit in a high-powered computer model.
This attack is mainly used to take over database servers. And, its late arrival on Figure 5. These layers are application, transport, network, data link, and physical. However, whereas the OSI model uses seven layers as shown in Figure 5.
Transport Layer The Transport Layer is a little bit removed from the user and it is hidden from the user. Its main purpose is to transport Application Layer messages that include Application Layer protocols in their headers between the host and the server. TCP provides a connection-oriented service and it guarantees delivery of all Application Layer packets to their destinations. It provides a no frills connectionless service with just delivery and no acknowledgments. But it is much more eicient and the protocol of choice for real-time data like streaming video and music. Network Layer The Network Layer moves packets, now called datagrams, from router to router along the path from a source host to a destination host.
The IP is the most widely used Network Layer protocol. IP uses header information from the Transport Layer protocols that include datagram Figure 5. The Best routes are found in the network by using routing algo- rithms. The standard IP address has been the so-called IPv4, a bit addressing scheme. But with the rapid growth of the Internet, there was fear of running out of addresses, so a new IPv6, a bit addressing scheme, was created. Data Link Layer The Data Link Layer provides the network with services that move pack- ets from one packet switch, like a router, to the next over connecting links.
This layer also offers reliable delivery of Network Layer packets over links. It is at the lowest level of communication and it includes the network interface card NIC and operating system OS protocols. The list of protocols in this layer include: Ethernet, ATM, and others like frame relay. The Data Link Layer protocol unit, the frame, may be moved over links from source to des- tination by different link layer protocols at different links along the way.
Physical Layer The Physical Layer is responsible for literally moving Data Link data- grams bit by bit over the links and between network elements. The protocols here depend on and use the characteristics of the link medium and the signals on the medium. Chapter 6 Anatomy of the Problem You have to do something to raise their level of awareness that they cannot be victims. With national critical systems on the line, sabotage should no longer be expected to come from only known high-tech and rich countries but from anywhere, the ghettos of Manila and the jungles of the Amazon included.
As computer know-how and use spreads around the world, so do the dan- gers of computer attacks. How on earth did we come to this point? We are a smart people that designed the computer, constructed the computer commu- nication network, and developed the protocols to support computer commu- nication, yet we cannot safeguard any of these jewels from attacks, misuse, and abuse. A detailed discussion of these explanations follows.
Computer Network Infrastructure Weaknesses and Vulnerabilities The cyberspace infrastructure, as we studied in Chapter 1, was developed without a well-conceived or understood plan with clear blueprints, but in reac- tion to the changing needs of developing communication between computing elements.