As the internet grows and technology evolves for modern computer networks, network security has become one of the most crucial factors for everyone. This includes everyone from end users and small and medium-sized businesses (SMBs) to cloud service providers.

Due to a growing volume of network attacks, network security should be a priority when designing network architecture. To understand the importance of this, imagine what could happen if there was a network integrity breach at a bank, stock exchange, or other financial database.

The importance of network security is not just limited to the IT industry. It is also important within industries such as health care. Health records contain some of the most valuable information available, including Social Security numbers, home addresses, and patient health histories. If this data is accessed by unauthorized persons, it can be stolen or sold to the black market.

Security awareness is important for everybody and not just the IT department. If you work with internet enabled devices, it's your responsibility too. However, you can only control information security once you know how to secure it.

No one can get into your system until something is compromised. Similarly, if your door is locked from the outside, nobody can enter your house unless they gain access to a duplicate key or have a similar key built by getting physical access to the lock. A few examples of how a system might be compromised are as follows:

• A targeted email could be sent to random users with an attachment (Drive by Download). If a user opened that attachment, their system would be compromised.
• An email is received which poses as a domain such as banking and asks you to change your password through a provided link. Once you do this, your username and password can be stolen.
• If a small typo is made when typing a website address into a browser, a similar page may open (Phishing) which is not genuine, and your credentials can be stolen.
• Features provided by websites for resetting forgotten passwords can also be very risky. Let's say somebody knows my email ID and attempts to access my account by selecting a forgotten password option. If the security question asks for my date of birth, this can easily be found on my resume.
• A password for an Excel file can easily be broken by a brute-force attack.
• The most widespread types of ransomware encrypt all or some of the data on your PC, and then ask for a large payment (the ransom) in order to restore access to your data.
• During DNS hijacking, an online attacker will override your computer's TCP/IP settings so that the DNS translation gets altered. For example, typing in abc.com will translate it into this IP: 140.166.226.26. However, a DNS hijacker will alter the translation so that abc.com will now send you the IP address of a different website.
• Denial of Service network attacks disrupt the normal volume of traffic sent to targeted services with excessive amounts of traffic. This can be damaging in various ways. One example could be if a company has a Friday sale, and a competitor launches an attack on them in order to shut their services down and consequently increase their own sales.

According to research by British insurance company Lloyd's, the damage from hacks cost businesses $400 billion a year.

To further explore the cost of cybercrimes, visit the following webpage:  https://www.forbes.com/sites/stevemorgan/2016/01/17/cyber-crime-costs-projected-to-reach-2-trillion-by-2019/#612db25c3a91.

The market research firm Gartner estimates that global spending on cybersecurity is somewhere around $96 billion in 2018. By 2020, companies around the world are expected to spend around $170 billion—a growth rate of nearly ten percent in the next five years.

Your data can be easily separated into the following three categories. This is especially important to know in order to determine the value of your data before planning for security:

• Low Business Impact (LBI): If LBI data is disclosed, limited information loss could occur. Examples of this kind of data include name, gender, and/or the country of residence.
• Moderate Business Impact (MBI): If MBI data is disclosed, disastrous information loss could occur, which directly damages the reputation of an organization. Examples of MBI data include first and last name, email ID, mailing address, and phone number.
• High Business Impact (HBI): If HBI data is disclosed, serious information loss could occur. Access and permission must be controlled and limited to a need-to-know basis. Examples of HBI data include government IDs, credit card information, medical health records, passwords, and real-time location.

Proper security control measures are required to ensure tight security. The following flowchart helps us to understand the security process:

• Risk Management Process: This is particularly important when designing a secure network. Risk management analysis must be done in advance as this aids designing secure infrastructure. Steps should include risk identification, risk analysis, risk ranking, and mitigation plans. For example, an ISP link can be a public or private Wide Area Network (WAN) connection. Data transfer between two sites over public infrastructure can be secured by implementing VPNs. Data transfer between two sites over private links can be future encrypted by link device. The purpose and funding of connection must be identified, and a proper risk assessment must be carried out before installing or activating any links.
• InfoSec Design Process: Perimeter boundaries must be defined and documented. For example, connecting to WAN internet or connecting to another location over WAN must be defined. When I say boundaries, we should always take a layered approach. There is no ideal situation to ensure 100% security, but by implementing security on every layer, you can ensure tight security. A layered security method encompasses both technological and non-technological safety measures.

  For example, perimeter security can be protected by firewalls. Infrastructure details, such as server type and services running on the system, must be identified. Software and operating system bugs should be documented. IP space and security zones should be defined. System admin access should be controlled by security groups.

• Verification process: The purpose of the verification process for each extranet/intranet connection is to generate all audit evidence documented in the compliance procedures of the security design. This will have information about users, remote IP, and tasks performed by them. Network scanning, penetration testing, and scorecard reporting provide an in-depth view of infrastructure security.

  A periodic audit is always required in order to know if there is unexpected activity.  Firewall logs, TCP/IP headers from load balancers on IIS, and two-factor authentications are examples of a verification process.

• Security implementation process: At this stage you should have the following items ready to be implemented:
  • Security policies—password policies and access control
  • Disaster recovery plan
  • Backup and recovery plan
  • WAN recovery plan
  • Network security zones
  • Database security
  • IIS or web security
  • Data and asset classification
  • Data encryption
  • Resource control for application users
  • Operating system security
  • Incident management and response
  • Change management and version control

Computer security is not all about end user computing, it also includes server/application infrastructure. For any data transfer between server and client, both ends should be secure. Even the communication channel should be secure enough to avoid data theft.

We know that professionals understand network security, but how about end users? We can force users to implement security strategies, but is that enough? For better security, awareness is key. Security issues are constantly being found with the software we use every day, including common and reliable programs such as Windows, Internet Explorer, and Adobe's PDF Reader. It is therefore very important that we take some simple steps towards becoming more secure.

People often think of computer security as something technical and complicated, but that is not strictly the case. In the following, we will explore the most basic and important things you should do in order to make yourself safer online:

• Use antivirus and antimalware and know which links are safe to click in emails
• Be careful about programs you download and run; don't trust your pop-up notifications
• On the server level, encryption chips can be used just to avoid physical theft of hardware

Most computer facilities continue to protect their physical assets far better than their data, even when the value of the data is several times greater than the value of the hardware.

Since awareness is especially important, we should also consider how much awareness we have within the organization. This can simply be achieved by sending a few emails that look genuine and getting the statistics of how many users opened such an email. Activities can be tracked in terms of number. For example, the statistics can be viewed for how many users shared their password and how many downloaded an attachment.

With today's complex network architecture and constantly growing networks, protecting data and maintaining confidentiality play a very important role. Complex networks consist of network traffic flowing between enterprise networks, data center networks and, of course, the cloud as well. A secure network helps us to protect against data loss, cyber-attacks and unauthorized access, thus providing a better user experience. Network security technologies equip multiple platforms with the ability to deal with the exact protection requirements.

A firewall is a network security appliance that accepts or rejects traffic flow based on configured rules and preconfigured policies. Placement of a firewall totally depends on the network architecture, which includes protection for network perimeters, subnets, and zones. Perimeter firewalls are always placed on a network's edge to filter packets entering the network. Perimeter firewalls are the first layer of security, and if malicious traffic has managed to bypass, host-based firewalls provide another layer of protection by allowing or denying packets coming into the end host device. This is called the multilayer security approach. Multiple firewalls can be set up to design a highly secure environment.

Firewalls are often deployed in other parts of the network to provide proper segmentation and data protection within enterprise infrastructure, on access layers and also in data centers.

Firewalls can be further classified as the following:

• Simple packet filtering
• Application proxy
• Stateful inspection firewalls
• Next-Generation Firewall

A traditional firewall provides functions such as Packet Address Translation (PAT), Network Address Translation (NAT), and Virtual Private Network (VPN). The basic characteristic of a traditional firewall is that it works according to the rules. For example, a user from subnet (10.10.10.0/24) wants to access Google DNS 8.8.8.8 on a UDP port 53.

A typical firewall rule will look like this:

However, Next-Generation Firewall works based on application and user-aware policies. Application-level control allows you to set policies depending on the user and the application.

For example, you can block peer-to-peer (P2P) downloads completely or disable Facebook chat without even blocking Facebook.

We will discuss firewalls in detail in upcoming chapters. The following diagram reflects zones and connectivity, which shows how firewall zones connect to multiple businesses:

• Demilitarized zone (DMZ): Internet-facing applications are located in DMZ. Other services on other zones remain inaccessible to the internet. The most common services placed in DMZ include email services, FTP servers, and web servers.
• Inside zone: The inside zone is known as the trusted zone to users. Applications in that area are considered highly secure. In the trusted area, security is maintained by denying all traffic from less trusted zones in any given firewall by default.
• Cloud and internet zone: Let's not focus on naming these. They are standard segments we see on an enterprise network. These zones are considered to be below security zones.

There is a high chance that attacks may enter a network. Intrusion prevention system (IPS) / Intrusion detection system (IDS) is a proactive measure to detect and identify suspicious or undesirable activities that indicate intrusion. In IDS, deployment can be online or offline, and the basic idea is to redirect traffic you wish to monitor. There are multiple methods like switch port SPAN or fiber optic TAP solution, which can be used to redirect traffic. Pattern matching is used to detect known attacks by their signature and anomalies. Based on the activity, monitoring alerts can be set up to notify the network administrator.

As the following diagram shows, SPAN port is configured on a switch in order to redirect traffic to the IDS sensor. An actual SPAN port creates a copy of data flowing for a specific interface and redirects it to another port on the switch:

IPS offers proactive detection and prevention against unwanted network traffic. In an inline placement of IPS, all the traffic will travel via IPS devices. Based on the rules, actions can then be taken. When a signature is detected on an IPS device it can be used for resetting, blocking, and denying connections, as well as logging, monitoring, and alarming. A system admin can also define a policy-based approach with defined policy violation rules and actions to keep in mind when well-known signatures are released. Actions should be defined by the system admin.

The following diagram shows a topology for inline setup of IPS. All the traffic travels through IPS devices for traffic inspection. This is a bit different to doing a port SPAN, since all data goes through an IPS box. Consequently, you should be aware of what type of data has to be inspected:

There are a number of different attack types that can be prevented using an IPS, including:

• Denial of Service
• Distributed Denial of Service
• Exploits
• Worms
• Viruses

Multitier topology gives you flexibility to segment resources based on role and access policies. In a typical three-layer application, architecture that has web, app, and DB servers can be distributed based on location. Since web/app zone is something always exposed to end users, Demilitarized Zone (DMZ) IP space is always public. Subnet and database servers should not be directly accessible, hence why we should always allocate private IP space from RFC 1918.

This offers gradual access to control, based on IPs and resource locations. When designing a network, you can introduce a multi-layer firewall approach. In a multiple layer design approach, the basic idea is to isolate resources from each other, considering the fact that if one layer is compromised then others are not impacted.

Cross-premises IPsec tunneling provides you with a way to establish secure connections between two networks and multiple on-premises sites, or other virtual networks in Azure/AWS. This can secure data transfer by encrypting your data via the IPsec encryption using the IPsec framework. Virtual networks in AWS are called VPC and, in Azure, VNET.

Distributed Denial of Service: A Denial-of-Service (DoS) attack or Distributed Denial-of-Service (DDoS) attack  is an attempt to make a network resource out of service to its targeted users.

The real-world target would be online services such as e-commerce and the gaming industry, preventing the shop from doing any business by making front resources unavailable for end users. Just think about a situation during big billion-day sales hours if someone launches a DDOS attack and makes your e-commerce portal shut down.

The two most basic types of DDoS attacks are as follows:

• WAN attacks: WAN DDoS attacks utilize available bandwidth on physical links with a high volume of packets with bigger payloads, or a high volume of packets with smaller payloads. Bigger payload network resources such as router or firewalls will process packets and consume all the bandwidth. With smaller payload network resources like routers, firewalls will try to process all the packets. However, due to limited CPU, cycle hardware resources won't be able to process genuine packets from end users and can fail under the load.

• For example, let's assume you have a 10 Mbps WAN link and during attack BW, utilization is just 5 Mbps. However, a number of small packets can reach one million packets per second. In this case, assume that your network gear has no CPU cycle to process all tiny packets

  Another example would be if someone launched a DDOS attack using a large ICMP packet. This can choke your bandwidth and leave no space for the rest of the application.

• The most common form of bandwidth attack is a packet-flooding attack, in which a large number of legitimate TCP, User Datagram Protocol (UDP), or Internet Control Message Protocol (ICMP) packets are directed to a targeted or aimed destination. Such attacks become more difficult to detect if attackers use techniques such as spoofing source addresses.

• Application attacks: These DDoS attacks use the expected behavior of protocols such as TCP and HTTP. Application attacks are disruptive but small and silent in nature and extremely hard to detect since they use expected behavior. Application-layer attacks are easy to generate and require fewer packets with a small payload to achieve out of services for targeted applications. Application attacks are focused on web-application layers. For a small HTTP request, the actual server has to execute a lot of resources on the web server to fetch the content or resources. Every such server resource will have limited CPU and memory and can be easily targeted. In this example, I am not considering cloud-based web applications, where you have elasticity features enabled and with growth in the number of requests, server resources are automatically created to accommodate such requests.

Let us understand more about this with the help of an example:  

• HTTP Floods: These are simple attacks in nature that try to access the same web page again and again in an automated fashion. They typically use the same range of IP addresses. Based on the trend, as this is being originated from the same source, the source pool can be blocked to mitigate attacks.
• Randomized HTTP Floods: These are complex attacks that use a large pool of IP addresses from multiple locations and randomize the URLs. Since these kind of attacks originate from multiple locations, it is not easy to block the source IP. However, the rate limit can be fixed on server resources.

To simplify, DDoS is a form of attack where multiple compromised networks/hosts are used to target a single system. This is like a zombie attack and it is very tough to identify genuine users. Once infected, the internet-connected devices become part of a botnet army, driving malicious traffic toward a given target.

These are the basic things you need to understand when you are working with online systems. When working with them day to day, we expose ourselves to risks.

Let's jump into the basic components of internet security.

Since we own internet enabled devices, we are responsible for our own security. So, let's begin with our passwords. As users, we must choose a strong password. Alternatively, organizations should encourage users to choose one.

Password analysis shows that quite a common password used by users is 123456 and other similar, simple patterns. Most users choose the same password across multiple platforms. If a server or database is compromised by hackers, it would be easy to crack passwords such as this.

Few common web portals contain personal information. However, if an employee is required to create a username consisting of their first and last name or employee ID, and this is combined with a simple default password such as abcX123, then their information is easy to guess.

The WannaCry ransomware attack was a worldwide cyberattack in May 2017 triggered by the WannaCry ransomware crypto worm. This attack targeted computers running the Microsoft Windows operating system by encrypting data and demanding ransom payments in the Bitcoin cryptocurrency. Such infection happens because people are running outdated software and attackers exploit this. This is not limited to PCs but also to mobile devices and other internet enabled devices.

Phishing is a form of online fraud where you receive an email that looks similar to a trusted source. The message may ask you to validate, confirm, or update your account information by logging into fake websites. Targets are contacted via telephone, email, and text message, which are used to extract credit card details and passwords.

This is my own email box, which contains a message stating that I am supposed to get 13,17422 INR, and I need to update my details. While the attacker is using money as a temptation tool, it is important to think instead about your IT return. Is this type of mail really to be expected from the IT department? You can easily guess that this is not a genuine domain just by looking at the email header. Following the instructions of this message can consequently have disastrous consequences:

Attackers might call you on the phone and offer to solve your computer problems by selling you a software license or by obtaining your personal information in order to update your details in a backend system.

Once they've gained your trust, cybercriminals might ask for your username and password or ask you to go to a website to install software that will let them access your computer in order to fix it. Once you do this, your computer and your personal information is hijacked.

In the same way, a banking fraud can take place. This includes cybercriminals calling you and trying to persuade you to share your credit card and banking details.

Some signs of phishing phone calls include:

• You have been specially selected for any offering
• You have won money in a lottery
• You have income tax refund
• Someone asking about credit card CVV and other details to update a banking database

Phishing attack protection requires steps to be taken by both users and enterprises. For users, awareness is the key. A spoofed message often contains some mistakes that expose its true identity. These can include spelling mistakes or changes to domain names, as seen in the earlier URL example. Users should also stop and think about why they're even receiving such an email or phone call.

You should report such emails to authorities so that appropriate actions can be taken.