Why Cybersecurity?

Cyber Security is important because the government, Corporate, medical organizations, collect military, financial, process, and store the unprecedented amount of data on a computer and other properties like personal information, and these private information exposure could have negative consequences. 

Cyber Security proper began in 1972 with a research project on ARPANET (The Advanced Research Projects Agency Network), a precursor to the internet. ARPANET developed protocols for remote computer networking. Example – If we shop from any online shopping website and share information like email id, address, and credit card details as well as saved on that website to enable a faster and hassle-free shopping experience, then the required information is stored on a server one day we receive an email which state that the eligibility for a special discount voucher from XXXXX (hacker use famous website Name like Flipkart, Amazon, etc.) website to receive the coupon code, and we will be asked to fill the details then we will use saved card account credentials. Then our data will be shared because we think it was just an account for the verification step, then they can wipe a substantial amount of money from our account. 

That is why Cyber Security provides services as a Security Gate-Way to make information more Secure; in today’s time, hackers are advanced. We can’t surely say whether the data stored in my Devices is safe from outside threats. With Cybercrime increasing rapidly, it’s crucial to have Cyber Security in place in our personal life and our Business.

Types of Cybersecurity:

1. Network Security – 

2. Application Security –

3. Information or Data Security:

4. Cloud Security –

5. Mobile Security –

6. Endpoint Security: 

1. Network Security – 

Focuses on securing computer networks from unauthorized access, data breaches, and other network-based threats. It involves technologies such as Firewalls, Intrusion detection systems (IDS), Virtual private networks (VPNs), and Network segmentation.

• Guard your internal network against outside threats with increased network security.
• Sometimes we used to utilize free Wi-Fi in public areas such as cafes, Malls, etc. With this activity, 3rd Party starts tracking your Phone over the internet. If you are using any payment gateway, then your bank account can be Empty.
• So, avoid using Free Network because free network Doesn’t support Securities.

2. Application Security –

Concerned with securing software applications and preventing vulnerabilities that could be exploited by attackers. It involves secure coding practices, regular software updates and patches, and application-level firewalls.

• Most of the Apps that we use on our Cell-phone are Secured and work under the rules and regulations of the Google Play Store.
• There are 3.553 million applications in Google Play, Apple App Store has 1.642 million, while Amazon App Store has 483 million available for users to download. When we have other choices, this does not mean that all apps are safe.
• Many of the apps pretend to be safe, but after taking all information from us, the app share the user information with the 3rd-party.
• The app must be installed from a trust-worthy platform, not from some 3rd party website in the form of APK (Android Application Package).

3. Information or Data Security: 

Focuses on protecting sensitive information from unauthorized access, disclosure, alteration, or destruction. It includes Encryption, Access controls, Data classification, and Data loss prevention (DLP) measures.

• Incident response refers to the process of detecting, analyzing, and responding to security incidents promptly.
• Promoting security awareness among users is essential for maintaining information security. It involves educating individuals about common security risks, best practices for handling sensitive information, and how to identify and respond to potential threats like phishing attacks or social engineering attempts.
• Encryption is the process of converting information into an unreadable format (ciphertext) to protect it from unauthorized access.

4. Cloud Security –

It involves securing data, applications, and infrastructure hosted on cloud platforms, and ensuring appropriate access controls, data protection, and compliance. It uses various cloud service providers such as AWS, Azure, Google Cloud, etc., to ensure security against multiple threats.

• Cloud base data storage has become a popular option over the last decade. It enhances privacy and saves data on the cloud, making it accessible from any device with proper authentication.
• These platforms are free to some extent if we want to save more data than we have to pay.
• AWS is also a new Technique that helps to run your business over the internet and provides security to your data

5. Mobile Security –

It involves securing the organizational and personal data stored on mobile devices such as cell phones, tablets, and other similar devices against various malicious threats. These threats are Unauthorized access, Device loss or Theft, Malware, etc.

• Mobile is the very common device for day to day work. Everything we access and do are from mobile phone. Ex- Online class, Personal Calls, Online Banking, UPI Payments, etc.
• Regularly backing up mobile device data is important to prevent data loss in case of theft, damage, or device failure.
• Mobile devices often connect to various networks, including public Wi-Fi, which can pose security risks. It is important to use secure networks whenever possible, such as encrypted Wi-Fi networks or cellular data connections.

6. Endpoint Security: 

Refers to securing individual devices such as computers, laptops, smartphones, and IoT devices. It includes antivirus software, intrusion prevention systems (IPS), device encryption, and regular software updates.

• Antivirus and Anti-malware software that scans and detects malicious software, such as Viruses, Worms, Trojans, and Ransomware. These tools identify and eliminate or quarantine malicious files, protecting the endpoint and the network from potential harm.
• Firewalls are essential components of endpoint security. They monitor and control incoming and outgoing network traffic, filtering out potentially malicious data packets.
• Keeping software and operating systems up to date with the latest security patches and updates is crucial for endpoint security.

5. Critical Infrastructure Security-

1. All of the physical and virtual resources, systems, and networks that are necessary for a society’s economics, security, or any combination of the above to run smoothly are referred to as critical infrastructure. Food and agricultural industries, as well as transportation systems, comprise critical infrastructure.
2. The infrastructure that is considered important might vary depending on a country’s particular demands, resources, and level of development, even though crucial infrastructure is comparable across all nations due to basic living requirements.
3. Industrial control systems (ICS), such as supervisory control and data acquisition (SCADA) systems, which are used to automate industrial operations in critical infrastructure industries, are frequently included in critical infrastructure. SCADA and other industrial control system attacks are very concerning. They have the capacity to seriously undermine critical infrastructure, including transportation, the supply of oil and gas, electrical grids, water distribution, and wastewater collection.
4. Due to the links and interdependence between infrastructure systems and sectors, the failure or blackout of one or more functions could have an immediate, detrimental effect on a number of sectors.

6. Internet of Things (IoT) Security-

1. Devices frequently run on old software, leaving them vulnerable to recently identified security vulnerabilities. This is generally the result of connectivity problems or the requirement for end users to manually download updates from a C&C center.
2. Manufacturers frequently ship Internet of Things (IoT) devices (such as home routers) with easily crackable passwords, which may have been left in place by suppliers and end users. These devices are easy targets for attackers using automated scripts for mass exploitation when they are left exposed to remote access.
3. APIs are frequently the subject of threats such as Man in the Middle (MITM), code injections (such as SQLI), and distributed denial of service (DDoS) attacks since they serve as a gateway to a C&C center. You can read more about the effects of attacks that target APIs here.

 

Computer Network Topologies

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A Network Topology is the arrangement with which computer systems or network devices are connected to each other. Topologies may define both physical and logical aspect of the network. Both logical and physical topologies could be same or different in a same network.

Point-to-Point

Point-to-point networks contains exactly two hosts such as computer, switches or routers, servers connected back to back using a single piece of cable. Often, the receiving end of one host is connected to sending end of the other and vice-versa.

If the hosts are connected point-to-point logically, then may have multiple intermediate devices. But the end hosts are unaware of underlying network and see each other as if they are connected directly.

Bus Topology

In case of Bus topology, all devices share single communication line or cable.Bus topology may have problem while multiple hosts sending data at the same time. Therefore, Bus topology either uses CSMA/CD technology or recognizes one host as Bus Master to solve the issue. It is one of the simple forms of networking where a failure of a device does not affect the other devices. But failure of the shared communication line can make all other devices stop functioning.

Both ends of the shared channel have line terminator. The data is sent in only one direction and as soon as it reaches the extreme end, the terminator removes the data from the line.

Star Topology

All hosts in Star topology are connected to a central device, known as hub device, using a point-to-point connection. That is, there exists a point to point connection between hosts and hub. The hub device can be any of the following:

• Layer-1 device such as hub or repeater
• Layer-2 device such as switch or bridge
• Layer-3 device such as router or gateway

As in Bus topology, hub acts as single point of failure. If hub fails, connectivity of all hosts to all other hosts fails. Every communication between hosts, takes place through only the hub.Star topology is not expensive as to connect one more host, only one cable is required and configuration is simple.

Ring Topology

In ring topology, each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send message to a host which is not adjacent to it, the data travels through all intermediate hosts. To connect one more host in the existing structure, the administrator may need only one more extra cable.

Failure of any host results in failure of the whole ring.Thus, every connection in the ring is a point of failure. There are methods which employ one more backup ring.

Mesh Topology

In this type of topology, a host is connected to one or multiple hosts.This topology has hosts in point-to-point connection with every other host or may also have hosts which are in point-to-point connection to few hosts only.

Hosts in Mesh topology also work as relay for other hosts which do not have direct point-to-point links. Mesh technology comes into two types:

• Full Mesh: All hosts have a point-to-point connection to every other host in the network. Thus for every new host n(n-1)/2 connections are required. It provides the most reliable network structure among all network topologies.
• Partially Mesh: Not all hosts have point-to-point connection to every other host. Hosts connect to each other in some arbitrarily fashion. This topology exists where we need to provide reliability to some hosts out of all.

Tree Topology

Also known as Hierarchical Topology, this is the most common form of network topology in use presently.This topology imitates as extended Star topology and inherits properties of bus topology.

This topology divides the network in to multiple levels/layers of network. Mainly in LANs, a network is bifurcated into three types of network devices. The lowermost is access-layer where computers are attached. The middle layer is known as distribution layer, which works as mediator between upper layer and lower layer. The highest layer is known as core layer, and is central point of the network, i.e. root of the tree from which all nodes fork.

All neighboring hosts have point-to-point connection between them.Similar to the Bus topology, if the root goes down, then the entire network suffers even.though it is not the single point of failure. Every connection serves as point of failure, failing of which divides the network into unreachable segment.

Daisy Chain

This topology connects all the hosts in a linear fashion. Similar to Ring topology, all hosts are connected to two hosts only, except the end hosts.Means, if the end hosts in daisy chain are connected then it represents Ring topology.

Each link in daisy chain topology represents single point of failure. Every link failure splits the network into two segments.Every intermediate host works as relay for its immediate hosts.

Hybrid Topology

A network structure whose design contains more than one topology is said to be hybrid topology. Hybrid topology inherits merits and demerits of all the incorporating topologies.

The above picture represents an arbitrarily hybrid topology. The combining topologies may contain attributes of Star, Ring, Bus, and Daisy-chain topologies. Most WANs are connected by means of Dual-Ring topology and networks connected to them are mostly Star topology networks. Internet is the best example of largest Hybrid topology

CPU SCHEDULING ALGORITHAM

 

Operating System Scheduling algorithms

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A Process Scheduler schedules different processes to be assigned to the CPU based on particular scheduling algorithms. There are six popular process scheduling algorithms which we are going to discuss in this chapter −

• First-Come, First-Served (FCFS) Scheduling
• Shortest-Job-Next (SJN) Scheduling
• Priority Scheduling
• Shortest Remaining Time
• Round Robin(RR) Scheduling
• Multiple-Level Queues Scheduling

These algorithms are either non-preemptive or preemptive. Non-preemptive algorithms are designed so that once a process enters the running state, it cannot be preempted until it completes its allotted time, whereas the preemptive scheduling is based on priority where a scheduler may preempt a low priority running process anytime when a high priority process enters into a ready state.

First Come First Serve (FCFS)

• Jobs are executed on first come, first serve basis.
• It is a non-preemptive, pre-emptive scheduling algorithm.
• Easy to understand and implement.
• Its implementation is based on FIFO queue.
• Poor in performance as average wait time is high.

Wait time of each process is as follows −

Process	Wait Time : Service Time - Arrival Time
P0	0 - 0 = 0
P1	5 - 1 = 4
P2	8 - 2 = 6
P3	16 - 3 = 13

Average Wait Time: (0+4+6+13) / 4 = 5.75

Shortest Job Next (SJN)

• This is also known as shortest job first, or SJF

• This is a non-preemptive, pre-emptive scheduling algorithm.

• Best approach to minimize waiting time.

• Easy to implement in Batch systems where required CPU time is known in advance.

• Impossible to implement in interactive systems where required CPU time is not known.

• The processer should know in advance how much time process will take.

Given: Table of processes, and their Arrival time, Execution time

Process	Arrival Time	Execution Time	Service Time
P0	0	5	0
P1	1	3	5
P2	2	8	14
P3	3	6	8

Waiting time of each process is as follows −

Process	Waiting Time
P0	0 - 0 = 0
P1	5 - 1 = 4
P2	14 - 2 = 12
P3	8 - 3 = 5

Average Wait Time: (0 + 4 + 12 + 5)/4 = 21 / 4 = 5.25

Priority Based Scheduling

• Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems.

• Each process is assigned a priority. Process with highest priority is to be executed first and so on.

• Processes with same priority are executed on first come first served basis.

• Priority can be decided based on memory requirements, time requirements or any other resource requirement.

Given: Table of processes, and their Arrival time, Execution time, and priority. Here we are considering 1 is the lowest priority.

Process	Arrival Time	Execution Time	Priority	Service Time
P0	0	5	1	0
P1	1	3	2	11
P2	2	8	1	14
P3	3	6	3	5

Waiting time of each process is as follows −

Process	Waiting Time
P0	0 - 0 = 0
P1	11 - 1 = 10
P2	14 - 2 = 12
P3	5 - 3 = 2

Average Wait Time: (0 + 10 + 12 + 2)/4 = 24 / 4 = 6

Shortest Remaining Time

• Shortest remaining time (SRT) is the preemptive version of the SJN algorithm.

• The processor is allocated to the job closest to completion but it can be preempted by a newer ready job with shorter time to completion.

• Impossible to implement in interactive systems where required CPU time is not known.

• It is often used in batch environments where short jobs need to give preference.

Round Robin Scheduling

• Round Robin is the preemptive process scheduling algorithm.

• Each process is provided a fix time to execute, it is called a quantum.

• Once a process is executed for a given time period, it is preempted and other process executes for a given time period.

• Context switching is used to save states of preempted processes.

Wait time of each process is as follows −

Process	Wait Time : Service Time - Arrival Time
P0	(0 - 0) + (12 - 3) = 9
P1	(3 - 1) = 2
P2	(6 - 2) + (14 - 9) + (20 - 17) = 12
P3	(9 - 3) + (17 - 12) = 11

Average Wait Time: (9+2+12+11) / 4 = 8.5

Multiple-Level Queues Scheduling

Multiple-level queues are not an independent scheduling algorithm. They make use of other existing algorithms to group and schedule jobs with common characteristics.

• Multiple queues are maintained for processes with common characteristics.
• Each queue can have its own scheduling algorithms.
• Priorities are assigned to each queue.

For example, CPU-bound jobs can be scheduled in one queue and all I/O-bound jobs in another queue. The Process Scheduler then alternately selects jobs from each queue and assigns them to the CPU based on the algorithm assigned to the queue.