IPv4 Address Class Ranges

IPv4 addresses are divided into five classes, each with a specific range and purpose. Here are the details:

Class A:

• Range: 1.0.0.0 to 126.0.0.0
• Purpose: Designed for very large networks.
• Private Range: 10.0.0.0 to 10.255.255.2551.

Class B:

• Range: 128.0.0.0 to 191.255.0.0
• Purpose: Suitable for medium-sized networks.
• Private Range: 172.16.0.0 to 172.31.255.2551.

Class C:

• Range: 192.0.0.0 to 223.255.255.0
• Purpose: Used for small networks.
• Private Range: 192.168.0.0 to 192.168.255.2551.

Class D:

• Range: 224.0.0.0 to 239.255.255.255
• Purpose: Reserved for multicast groups.

Class E:

• Range: 240.0.0.0 to 255.255.255.255
• Purpose: Reserved for experimental use.

These classes help organize and allocate IP addresses efficiently across different types of networks.

You can use Class A, B, or C on your internal network regardless of its size. These are just recommendations.

This is covered in A+, Network+, and Server+.

 APFS (Apple File System)

Apple File System (APFS) is a file system that's used for encryption, data storage, and file sharing on Apple devices:

Encryption

APFS uses advanced encryption technology to protect data from unauthorized access.

Data storage

APFS is optimized for solid-state drives (SSDs) used in most modern Mac computers. APFS allocates storage space on demand and can share space between multiple volumes within a container.

File sharing

APFS allows users to duplicate files instantaneously, so the duplicate doesn't take up more storage space.

APFS is the default file system for Mac computers running macOS 10.13 or later. It is also used on iOS, tvOS, and watchOS. APFS is generally considered the better choice for Mac users, but exFAT might be more suitable if you need to share files with Windows computers.

ext3 & ext4

 ext3 vs ext4

Ext4 is an advanced version of the ext3 file system for Linux that offers several improvements, including:

File and partition sizes:

Ext4 supports files up to 16 terabytes and partitions up to 1 exabyte, while ext3 supports files up to 2 terabytes and partitions up to 16 terabytes.

Sub-directories:

Ext4 supports unlimited sub-directories, while ext3 only supports up to 32,000.

Performance:

Ext4 is faster due to extents, contiguous blocks of data, and delayed allocation, which optimizes write operations.

Reliability:

Ext4 is more reliable due to checksums for the journal and metadata, as well as multi-block allocation.

Flexibility:

Ext4 has more flexibility with subvolumes and online defragmentation.

Scalability:

Ext4 is designed to support large file systems and keep up with increasing disk capacities.

Ext3 was the default file system for many Linux distributions, but ext4 is now the default for many.

 ExFat File System

ExFAT (Extended File Allocation Table) is a file system used for storing data on devices like flash drives, digital cameras, and mobile phones:

Storage capacity

ExFAT can store larger files than the FAT32 file system, with a 4 GB file size limit.

Compatibility

ExFAT is compatible with most Windows and Mac operating systems, though older versions may need an update.

Default file system

ExFAT is the default file system for SDXC and SDUC cards larger than 32 GB.

Other devices

ExFAT is also used in smart televisions, portable music and video players, and media centers.

Some things to keep in mind about exFAT include:

Not journaled

ExFAT is not journaled, so if you eject the drive incorrectly while reading or writing, you might lose data or corrupt the drive.

Not compatible with some older devices

ExFAT isn't compatible with some older devices.

Not suitable for intensive applications

ExFAT can have problems with intensive applications, and it can take several attempts to transfer data correctly.

Data loss

Since exFAT doesn't redundantly store master data, you should carefully remove storage media with the exFAT file system.

 Security Groups

Security groups can be used to control access to resources and data and to manage network traffic:

Control access

Security groups can grant users access to applications, actions, and data. For example, in Active Directory, you can assign user rights to security groups (RBAC) to determine what group members can do.

Manage network traffic

Security groups can be used to control the traffic that can reach and leave resources. For example, in AWS, you can create security groups with inbound and outbound rules to control traffic to and from an EC2 instance.

Protect against threats

Security groups can be used to protect against threats like credential theft, fraud, and brand impersonation.

Here are some examples of how security groups can be used:

Google Admin console

To make a group a security group, you can add the Security label to it in the Google Admin console.

Azure application security groups

You can group virtual machines and define network security policies based on those groups.

AWS security groups

You can create security groups with inbound and outbound rules to control traffic to and from an EC2 instance (Virtual Machine).

 Digitizer

A digitizer is a device that allows users to input drawings, sketches, and handwritten notes into a computer. It's also a graphics tablet, drawing tablet, or pen tablet.

A digitizer has a pressure-sensitive flat surface and a stylus or pen-like instrument that users draw or write with. The digitizer's sensors detect the stylus's movements and pressure levels and send the data to the computer. The computer then processes the data and translates it into visual elements on the screen.

Digitizers are used for many purposes, including:

• Drawing and painting: Digitizers can recreate the drawing experience with a pen on paper.
• Creating and editing notes: Digitizers can create and edit handwritten notes or text documents.
• Digital signatures: Digitizers are a base component of many digital signature technologies.

On a laptop, a touchscreen digitizer is an additional screen that sits on top of the laptop's LCD screen. There are two types of touchscreen laptops:

• Standard LCD with separate digitizer glass: The LCD displays the image, and the digitizer glass responds to touch.
• Embedded touchscreen: The touch is embedded into the LCD during manufacturing.

 Data Masking

Data masking is a cybersecurity technique that protects sensitive data by replacing it with artificial but realistic versions. It's also known as data anonymization, obfuscation, redaction, or scrubbing.

Data masking is essential because it:

• Protects sensitive data: It safeguards confidential information like financial records, personally identifiable information (PII), or proprietary business data.
• Complies with regulations: It helps organizations meet data protection regulations.
• Maintains data privacy: It allows organizations to use their data for operational purposes while keeping sensitive information private.
• Preserves data integrity: It preserves the original dataset's integrity.

Here are some techniques used in data masking:

Substitution

Replaces data with similar values. For example, a user's actual name can be replaced with a fake name.

Reorganization

Randomly rearranges characters to replace the original content. For example, an ID number in a production database could be replaced by a different number in a test database.

Example

Name: J***** H******

Data masking is typically used with other security measures, such as access controls, encryption, and auditing.