The Great Wall O' Notes

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Table of Contents


My Custom Resources

Quizlet: Encryption Algorithms (Security+) Quizlet: Comptia A+ and Network+ Standards Quizlet: 802.11 Standards

Other Recommended Resources

A+ Cert Prep by Mike Meyers and Total Seminars Security+ Cert Prep on LinkedIn Free Comptia Exam Courses by Professor Messer Free Comptia Network+ Course by Dark Bird Tech Free subnetting practice questions Free Comptia practice exams Various Comptia Practice Exams on LinkedIn Learning

Windows 10 Editions

Home Edition
Pro
Pro for Workstations
Enterprise Edition
Remote Desktop
Client only
Client and Host
Client and Host
Client and Host
Bitlocker
No
Yes
Yes
Yes
Join a Windows Domain
No
Yes
Yes
Yes
Group Policy Management
No
Yes
Yes
Yes
Max. Physical CPUs
1
2
4
2
Max. Physical RAM (x64)
128 GB
2 TB
6 TB
6 TB
ReFS Support
No
No
Yes
Yes
Volume licensing
No
No
No
Yes
AppLocker
No
No
No
Yes
BranchCache (remote site file caching)
No
No
No
Yes
Granular User Experience (UX) control
No
No
No
Yes

Windows 10 Minimum Requirements

Windows 10 x86
Windows 10 x64
CPU
1 GHz processor or faster
Memory
1 GB
2 GB
Storage
32 GB
GPU
Microsoft DirectX 9 graphics device with WDDM driver, min. res. of 800 x 600

Windows CLI

Netstat

Netstat displays network statistics on many different OS.
Switch
Description
-a
Shows all active connections
-b
Displays executable name responsible for the connection or listening port. Requires elevation.
-n
Does not resolve names, including those of ports.

Net

Net is a combination of many different windows network commands.
Subcommand
Description
view
Used to view available network shares.
use
Map a network share to a drive letter.
user
View user account information and reset passwords

Chkdsk

Chkdsk is a command that checks the file system and file system metadata of a volume for logical and physical errors.
Switch
Descriptions
/f
Fixes errors on the disk.
/r
Locates bad sectors and recovers readable information.
/perf
Uses more system resources to complete a scan as fast as possible.

Sfc

Sfc scans and verifies the integrity of all protected system files and replaces incorrect versions with correct versions.
Switch
Description
/scannow
Scans the integrity of all protected system files and repairs files with problems when possible.
/verifyonly
Scans the integrity of all protected system files without performing repairs.
/scanfile [file]
Scans the integrity of the specified file (full path) and attempts to repair any problems if they're detected.

WinRE

Windows Recovery Tools

To access the Windows Recovery Environment, shift-click on restart or find Advanced startup in settings. Alternatively, you can access it by booting from installation media and clicking "Repair my PC."
Name
Description
Reset this PC
This option reinstalls Windows and gives you the option to either keep or remove personal files.
System Restore
This option allows you to go back to a restore point. Do note that restore points to do not affect personal files.
Startup Repair
This tool will attempt to automatically diagnose and solve common issues.
Uninstall Updates
This will allow you to uninstall recent quality or feature Windows updates.
System Image Recovery
This option allows you to restore from a system image.
Startup Settings
Startup Settings allows you to choose different boot settings, such as low-resolution video and safe mode.

Windows Startup Settings

Setting
Description
Enable low-resolution video
This option uses a low-res but reliable video driver stuck at a resolution of 800 x 600. This can be helpful if something has gone wrong with your regular video drivers.
Enable Safe Mode
Safe mode disables many features and leaves a rather bare-bones version of Windows. It can be useful for fixing bad drivers.
Enable Safe Mode with Networking
Does the same thing as safe mode but with networking abilities.

File Systems

File system
Max. Volume Size
Max. File Size
Features
Operating System
FAT32 (File Allocation Table)
2 TB
4 GB
N/A
N/A
exFAT (Extended File Allocation Table)
2 TB
16 EB
Made for flash drives.
Windows, compatible with many.
NTFS (NT File System)
8 PB
16 EB
Quotas, file compression, encryption, symbolic links, large file support, security, and recoverability.
Windows. Limited compatibility.
ext3 (Third extended file system)
4-32 TB
16 GB to 2 TB
N/A
Wide compatibility, common in Linux OS.
ext4 (Fourth extended file system)
1 EB
16 TB
N/A
Wide compatibility, common in Linux and Android OS.
APFS (Apple File System)
N/A
8 EB
Optimized for SSDs. Encryption, snapshots, and increased data integrity.
Apple OSes only.

macOS

Mac File Types

Name
Description
.dmg
Apple disk image, mountable as a drive in Finder.
.pkg
Similar to an .exe. It's an installer package used to distribute software. It runs an installer script.
.app
Application bundle. It contains all the necessary files to use the application. With .app files, moving an app is as simple as moving the file. In Finder, you can use the "view package contents" option to see the .app file's contents. To uninstall, move the file to the trash or run an uninstaller app.

System Preferences

Name
Description
Displays
Configure the relative location of multiple displays, select which display gets the menu (not restricted to primary), modify individual display settings such as resolution, color profiles, and brightness.
Network
Configure network interfaces, IP addresses, DHCP, DNS, 802.1X, and more.
Printers & Scanners
Add or remove printers + scanners, share printers/scanners, and if supported, view supply levels.
Privacy
Limit application access to private data such as location, photos, and calendars. Also controls app access to camera and microphone. Unauthorized apps can't view private data, including malware. That functionality must be manually enabled.
Accessibility
Allows apps to use system input, useful for accessibility apps. Also controls access to scripting per app.
Time machine
See mac features entry.

Mac Features

Name
Description
App store
Used for updating apps as well as the OS.
Apple ID and corporate restrictions
Personal Apple products use a personal Apple ID associated with personal data and purchases. Companies use Managed Apple IDs. These allow for AD integration, connecting with MDMs, and managing the user's apps and digital content.
Time Machine
Mac's built-in backup feature. It keeps hourly backups for 24 hours, daily backups for a month, and weekly backups until space runs out. When space runs out, the oldest backups are deleted as needed.
Anti-virus
MacOS does not come with anti-malware, however you can install third-party anti-malware. Malware is quite uncommon for macOS systems, but it's becoming more prevalent as macOS gets more popular.
System Preferences
Mac equivalent of Control Panel. Provides access to most customization and personalization options, including important configuration utilities.
Mission Control
Used to quickly view every window that's running. Activated by swiping up with three fingers or Control-Up arrow. Similar to Task View in Windows.
Spaces
Tasks separated into different virtual desktops.
Keychain
Built-in password management. Allows autofill with permission. Everything is encrypted, and the encryption key is the password.
Spotlight
Used to search for files, apps, images, and other files. Accessed using command-space or clicking the magnifying glass in the upper-right. Categories can be configured in system preferences.
ICloud
Integrates apple technologies, allowing you to share calendars, photos, docs, contacts, etc. between devices. Also used to backup devices and share files.
Gestures
Much like windows laptops, macOS has customizable touchpad gestures built-in.
Finder
The file manager of macOS. Also has file servers, remote storage, and screen sharing integrated into it.
Remote Disc
Allows you to use the optical drive of another device. Does not work with audio CDs or video DVDs. You can set up sharing in System Preferences.
Dock
Fast access to apps and folders. Basically the same as the taskbar.
Disk Utility
Manage disks and images. Modify partitions, troubleshoot file systems, and erase disks. Create, convert, and restore images.
FileVault
Does full disk encryption (FDE). Proper authentication is required before maxOS can start. Available in System Preferences.
Terminal
Command line access to the operating system.
Force Quit
Access force quit using command-option-escape. Used to force quite an application.

Linux

Misc Commands

Name
Description
Syntax
more
Paginates the results of other commands.
[command] | more
pwd
Prints the working directory path.
pwd
chmod
Changes the mode of the file object. See Linux Permissions for more.
chmod [mode] [file]
chmod [user][+/-][r/w/x] [file]
apt-get
Advanced Packaging Tool. Handles the management of application packages in Debian-based distros.
apt-get [options] [command] [packages]
yum
Yellowdog Updater, Modified. Handles the management of RPM packages for Red Hat-based distros.
yum [command] [subcommand]
ps
View running processes and their corresponding PIDs. Similar to the proccesses section of Task Manager.
ps [options]
top
View CPU, RAM, and resource utilizations. Much more similar to task manager compared to ps.
top [options]
find
Used to search a directory + subdirectories for a file.
find [directory] -name [filename]
dig
Lookup information from DNS servers. It can respond with a FQDN or IP address.
dig [FQDN/address]

Linux permissions

When working with linux permissions, r=read, w=write, and x=execute. Permissions have three sections, one for the owner, for the group, and others (in that order.) But there's an additional column before those section which indicates the file type. Simple files like txts have a -, directories have a d, and symbolic links (similar to shortcuts) have an s. There are other options, but these are the most common.

The sections each have three columns, first for r, then for w, then for x, in that order. The column can contain either its corresponding letter if that permission is enabled or a dash if it is not.

So, for example, a file with a mode of -rwxr--r-- is a regular file, the owner has all permissions, while the group and other users only have the read permission. A file with a mode of drwxr-xr-x is a directory that the owner has all permissions to, while the group and others can only read or execute.

Linux permissions also have corresponding numbers. Execute=1, write=2, and read=4. You can add these together to get a particular combination of permissions. Therefore, read and write is 6, while read and execute is 5. This functions as a shorcut when using chmod, allowing you to specify a mode of 754, corresponding with [-]rwxr-xr--, allowing the owner all permissions, the group read and execute permissions, and all other users read only permissions.

Read
Write
Execute
Read
4
6
5
Write
6
2
3
Execute
5
3
1
Read, write, execute
7

Linux Features

These features may or may not be a included with certain distributions. If they are not, you can install them with apt-get or yum.
Name
Description
tar
A backup utility. The name stands for Tape Archive. It's a command-line utility, making it easy to script and schedule.
rsync
Another utility used to sync files on a storage device to another storage device. Anything you change on the source device will also be changed on the destination device.
Clam antivirus
An open source antivirus engine.
Samba
Adds SMB features to linux, such as sharing files and printers and Active Directory Integration.

Types of Malware

Name
Description
Trojan horse
Also just known as Trojans, this malware's goal is to disguise itself as something helpful or entertaining. If the user falls for its trick and runs it and no anti-virus detects it, it will have circumvented their security entirely, allowing it to do basically whatever it wants with the system. It may even intall additional malware!
Rootkits
This type of malware originated in Unix systems, hence the word "root" in rootkit. Rootkits embed themselves deep within the OS's files, even within the kernel itself. As a result, it may be undetectable by the OS, because the OS believes it to be part of its own files. For example, you may not see it in Task Manager even when it's running. This also means it's invisible to normal anti-virus software. To deal with rootkits, first identify symptoms or abnormalities. If you're able to identify the specific rookit, use a remover built specifically for that rookit. The prevent rootkits, use Secure Boot in the UEFI.
Virus
A virus is a type of malware that replicates itself, but needs human intervention, such as a human running the virus software. The virus may replicate itself through a variety of means, such as through the network or onto any connected storage media. Viruses may be very obvious or very subtle.
Boot sector virus
This type of malware becomes part of the boot sector in order to boot before the operating system does, therefore, anti-virus software is unable to stop it. To protect against boot sector viruses, enable Secure Boot in the BIOS.
Keyloggers
Keyloggers do exactly what they sound like: they everything a user types on their keyboard. This gives attackers easy access to sensitive information such as passwords and private messages. Keyloggers can also capture other data such as clipboard data.
Ransomware
This type of malware encrypts all personal files without encrypting OS files. It then displays a screen explaining that all of the files have been encrypted and the user must pay the attacker in order to decrypt them. A smart attacker will force the user to use an untraceable payment method such as bitcoin so they don't get caught.

Troubleshooting

Troubleshooting Windows

Name
Cause
Description
BSODs and frequent shutdowns
These symptoms can be caused by many issues, including bad hardware, drivers, or applications.
If you believe the issue is software-related, try using System Restore or rolling back a driver. If you're unable to get to the desktop, try using Safe mode.
If you think the BSOD may be hardware-related, try reseating or removing the hardware. You can also try using hardware diagnostics which may be provided by the manufacturer or built into the BIOS.
Sluggish performance
Sluggish performance is caused by a system not having enough resources or its resources being overused.
When facing a sluggish system, try using Task Manager to find any processes with high CPU utilization. Also check Windows Update for any available patches, make sure to check for available disk space and defragment the drive if it's an HDD, and in the case of Laptops, check to see if it's using power-saving mode, which throttles the CPU and results in slower performance. Also ensure that the fans and vents of the system are clear, and consider the possibility of malware being the cause. You may want to run a scan with anti-malware software.
Boot errors: "Operating system not found," "Missing operating system"
These errors can be caused by a boot loader (the code within the boot sector that starts the OS) being replaced or changed, or trying to boot from a non-bootable drive.
This issue can be fixed by ensuring that there's no removable media connected and that the drive you do want to connect to is properly connected. If there's an issue with the bootloader, you can try fixing it with Startup Repair or bootrec /rebuildbcd.
Missing NTLDR
This issue means that the main windows boot loader is missing. It could be caused by the file being missing or corrupted or by the system trying to boot into the wrong drive.
The issue can be fixed by using Startup Repair, replacing the file manually by copying it from another system, or disconnecting removable media.
Boots to Safe Mode
For this issue, use Startup Repair.
Certain hardware not starting
This issue is often caused by a bad driver.
To fix, check Device Manager to manage drivers and Event Viewer to check logs.
"One or more services failed to start"
This issue is associated with bad drivers or hardware.
To fix, first try starting the service manually, then check account permissions to see if it has permissions to run, then confirm that you have its dependencies. If it's a windows service and it's still not working, you should also check system files. Otherwise, if it's an application service, try reinstalling the application.
Application crashes
To find the cause of and prevent further application crashes, check the Event Log for more information as well as the Reliability Monitor. You can also try reinstalling the application.
Low memory warnings
This is caused by memory being overused.
To resolve this issue, install more RAM, close memory-intensive processes, or increase virtual memory.
USB controller resource warnings
USB controllers support different numbers of endpoints. USB devices require certain numbers of endpoints. When you see this warning, the controller doesn't have enough endpoints for the device.
One solution is to move the device to a different interface and try to match the interface version to the device version.
System instability
This is characterized when a system has a lot of issues in several categories. For example, software errors, system hanging, and crashes. These issues could be caused by basically anything.
Because the cause of these issues is so enigmatic, it's probably best to start with a full diagnostic, testing everything from the ground up. Starting with hardware, using manufacturer-provided diagnostics, storage and memory checks, then onto software diagnostics, such as SFC and running anti-malware scans.
Slow profile load
This issue may be caused by network latency on the path to the domain controller or the client workstation choosing a remote domain controller instead of a local one.
This issue can be fixed by reducing latency or contacting the administrator of the remote domain controller and seeing if there's a way to redirect the workstation to the local domain controller.
Time drift
Naturally, a computer's internal clock will drift over time.
To solve this issue, set the machine to sync automatically or manually.

Troubleshooting Solutions

Solution
Description
Rebooting
This is a common first step and it's effective because it clears out ram, allowing software to start somewhat fresh. It's a good technique when dealing with memory leaks, apps using too many resources, or even bugs in a router's OS.
Restarting Services
Services can have the same issues as normal processes, such as memory leaks or crashes. They can be restarted using Task Manager or the Services tool.
Updating Apps
If an app isn't working properly, it may need to be updated. Some apps will have automatic updaters, while others will require you to go to the manufacturer's website and download the update manually.
Repairing apps
If you're sure your app is up to date and it's still not working, you can also try using the repair option in the Apps & features settings. This tool can install missing files, replace corrupted ones, fix shortcuts, repair registry files, and update or reconfigure drivers.
Resetting apps
This is another Apps & features option. If repair is unavailable or doesn't work, reset is your next best option. It removes all application data, but doesn't make any changes to the app installation itself.
Uninstalling/Reinstalling apps
This is the final Apps & features option. It removes the app, which allows you to then reinstall it, which may help with issues such as improper installation.
Verify requirements
You may want to check an app's minimum requirements to ensure that you have the right hardware to run it.
Rebuild Windows Profiles
If you get errors such as "The User Profile Service failed the logon. User Profile cannot be loaded." or apparently missing user documents, you need to delete that user's profile so Window's will rebuild it. To do this, first login as a Domain Administrator. Then, rename the user's \Users\name folder. This will prevent those files from being deleted during this process. Next, backup user registries (HKLM\SOFWARE\Microsoft\Windows NT\CurrentVersion\ProfileList > Right-click > Export) and delete this particular user's registry entry. Login as this user so their profile will be rebuilt (and also recreat the Users\name folder), then go back to admin and copy over important files from the old profile. Be careful what you copy, as some files may be corrupted.

Troubleshooting Mobile Devices

Issue
Solution
Apps are running slowly or not loading at all.
If the app is running, try force stopping it. The process for this varies on the device. If that doesn't help, restart the phone. If none of that helps, it may be an issue with the app itself. You should check to see if there are any updates for the app available.
App hangs or crashes.
Try restarting the phone, updating the app, or uninstalling and reinstalling the app.
App fails to update, but other apps can update just fine.
If you have the app set to update automatically, try updating it manually. Otherwise, restart the phone.
OS will not update.
Check available storage and remove unused apps and files. Check your connection. You may want to connect to Wi-Fi instead of cellular. You may also want to try connecting to a different network in order to use a route to the update server that has less traffic. If all else fails, reboot.
Battery life issues may be caused by being in an area with bad reception. It can also be caused by an aging battery, as phone batteries can only last so long.
You can preserve battery life by disabling unnecessary features such as Wi-Fi, bluetooth, and GPS and/or enabling airplane mode. If the device is getting on in years, you may also want to replace the battery or the device itself. You can also check application battery usage to help make decisions about what apps to use.
Random reboots. This is when the device reboots, seemingly out of the blue, during normal operation.
Check to make sure the OS and apps are up to date. You can also try performing a hardware check, although your options are limited with mobile devices. You can also contact tech support for the phone, as they have access to crash logs on the device.
Connectivity issues
In the case of intermittent connectivity, try moving closer to the access point or trying a different access point. In the case of no Wi-Fi connectivity, make sure the Wi-Fi feature is enabled, ensure you've provided the right password to the network, or rebooting the device. In the case of no Bluetooth connectivity, make sure Bluetooth is enabled, make sure the Bluetooth devices are paired, and try rebooting. In the case that NFC isn't working, make sure NFC is enabled, reboot the device, and if it's payment-related, try removing and adding the card you're trying to use. In the case that AirDrop isn't working, make sure the devices aren't further than 30 feet apart, turn on Wi-Fi and Blueooth, and check your AirDrop discovery options.

Troubleshooting Security Issues

Issue
Details
Solution
Malware
Some symptoms of malware include slow performance or lock-ups, internet connectivity issues (to allow the malware more control), and OS update failures.
If you have decent backups, it's best to recover from a known good backup. This will ensure that all malware is fully wiped. Otherwise, you can use a malware cleaner to attempt to remove the malware.
Malicious notifications
If you allow notifications from the wrong sites, they might send you notifications claiming that you have malware or that your antivirus is out of date.
To resolve this issue, disable notifications from the offending site. You may also want to run a malware scan if you think you might actually have malware.
False antivirus alerts
This type of malware pretends to be a legitimate antivirus program and gives you false warnings that you have malware. In reality, the only malware is the app itself. Some of these apps can be very convincing, but some warning signs are requiring you to call unofficial numbers or requiring money to "unlock" your pc or subscribe to their services.
This type of malware is often made skillfully and requires specific removal utilities or techniques.
Altered system or personal files
Renamed system files, disappearing or encrypted fiels, permission changes, and/or access denied to files. These are additional malware symptoms.
To fix this issue, follow normal malware removal techniques such as trusted malware cleaners or restoring from a known good backup.
Browser security alers
Security alerts and invalid certificates.
Check the certificate's details and the details of the error shown. Different errors are more concerning than others. Also be sure to check that your system's time and date is correct.
Browser redirection
This is when you try to go to a website and instead get redirected to a different website. For example, you might type in a google search and wind up somewhere else entirely. The most common cause of this issue is malware.
Clean the malware or restore from a known good backup.

Managing Backups

Backup Types

Name
Description
Benefits
Downsides
Full backup
A backup that includes everything, from OS files to user files.
- Everything can be restored from a single backup.
- Low restore time.
- Long backup time.
- Takes a lot of storage space.
Differential backup
After creating a full backup, make subsequent backups containing data that's changed since making the full backup.
- More practical in terms of daily use.
- Requires not only a full backup but also the most recent differential backup in order to restore.
Incremental backup
After creating a full backup, subsequent backups include data changed since the full backup as well as data changed since the most recent incremental backup.
- Even more practical for everyday use due to the likelihood of smaller backups.
- Low backup time.
- Requires the last full backup as well as all previous incremental backups.
- High restore time.
Synthetic backup
When a full backup is combined with subsequent incremental backups.
- Faster.
- Less bandwidth intensive.
- The efficiency of an incremental backup.
- The singularity of a full backup.
- Nothing. They are amazing.

Backup Techniques

Name
Description
Grandfather-Father-Son
GFS is a technique for backups in which 1 full backup is made per month (grandfather), another full backup is made once per week (father), and an incremental or differential backup is made per day (son.) Grandfather backups are a good choice for off-site storage.
3-2-1 Backups
3 copies of data should always be available. 2 different types of media should be used. 1 copy should be kept off-site. 3 copies, 2 medias, 1 off-site.

Example

Let's say The Company does one full backup each month and stores it on the cloud, does a weekly full backup and stores it on a flash drive, and also does incremental backups each day, also stored on flash drives. This is an example of both backup techniques being used in conjunction with each other.

On the Job

Change Management Process

Step
Description
Change request forms
Paperwork outlining the change is filled out and usually available through an online system. This process is usually transparent and many groups and people are involved.
Purpose of the change
Define the reason for the change. There must be a good reason to make the change, as making changes costs time and/or money.
Scope of the change
Define the scope of the change. For example, is it limited to one server, or maybe it affects an entire site? Does it impact applications, networks, customer access? And how long will it take to implement?
Risk analysis
What could go wrong if the change doesn't work as expected? And on the contrary, what's the risk of NOT making the change? This could be relevent when it comes to security patches, for example.
Change board and approvals
The change board will assess the change request and determine if the change should be implemented, the priority of the change, etc.
End-user acceptance
The end-users see the change and hopefully are satisfied with it.

Miscellaneous Business Terms

Name
Definition
Procurement life cycle
The process of purchasing a resource from a supplier. It starts with formal request from the user, involves negotiation with the supplier, and ends in exchanging payment and product.
Acceptable use policies (AUP)
Document detailing the appropriate use of company assets, may cover many electronic devices. It may be used to limit legal liability.
Network topology diagram
Describes the network layout, may also be a logical diagram. It may also have physical details such as server rack locations.
Compliance
Following necessary laws, standards, and policies, which may be industry-specific.
Splash screens
Any screen that appears immediately after running or signing into an application. It may simply be a logo or illustration, or it can be more informational. It may include warnings or disclaimers.
Incident reports
Documentation when any sort of incident occurs. What counts as an "incident" depends on the company.

Safety

Electrostatic Discharge

Do
Don't
Do maintain a humidity level over 60%.
Don't leave the power connection of a device you're working on plugged in.
Do touch the metal chassis of a system to equilize yourself with it.
Do NOT connect yourself to the ground of an electrical system.

General safety

Do
Don't
Do disconnect all power sources before working on a device.
Don't touch anything if you aren't sure it's safe to do so.
Do replace entire power supply units.
Don't try to repair the internal components of a power supply.
Do connect devices that you aren't working on to the ground.
Don't ever connect yourself to the ground.
Do lift with your legs and keep your back straight.
Don't carry items that are too heavy.
Do use equipment to help carry heavy items.
Don't use water or foam to quell electrical fires.
Do use carbon dioxide, FM-200, or other dry chemicals to extinguish an electrical fire.
Don't forget to follow health and environment regulations!
Do remove the power source from an electrical fire when possible.
Do wear safety goggles and/or an air filtering mask when appropriate.

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