CompTIA® A+ Practical Certification Exam Cram Notes

4. Software Troubleshooting

4.1 Troubleshooting PC operating system problems with appropriate tools

Windows RE (Short for Recovery) is new for Windows 7/8/10 and completely replaces the recovery console in Windows XP. You should be able to perform most tasks of recovery console from Windows RE.

Windows RE (Recovery Environment) is stored as winre.wim file on device hard drive or SSD in Windows 7, 8/8.1 and 10. Windows 7 normally keeps it on the same partition/volume with Windows, while Windows 8 and later usually keep it on the hidden System Reserved partition that also contains boot files and Boot Configuration Data (BCD).

Microsoft recommends that you regularly create Automated System Recovery (ASR) sets as part of an overall plan for system recovery so that you are prepared if the system fails. ASR should be a last resort for system recovery. Use ASR only after you have exhausted other options. For example, you should first try Safe Mode Boot and Last Known Good.

A hard disk should never be low level formatted at the customer premises. It is highly recommended that it is done at the manufacturer's or at any authorized center.

To get into the Windows Vista and Windows 7 Safe Mode, as the computer is booting press and hold your "F8 Key" which should bring up the "Windows Advanced Options Menu" . Use the arrow keys to move to "Safe Mode" and press Enter key.

Since Windows 7/8/10, Microsoft added a new security feature called User Account Control (UAC). It tries to prevent malicious apps from doing potentially harmful things on your PC. Before the administrator-level (elevated) action is allowed, UAC asks permission from the user to go ahead with it, or cancel the request.

How to change UAC settings in Windows 7

1. Open the Windows Control Panel, and then click System and Security.

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2. The System and Security window appears. Click Action Center.

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3. The Action Center window appears. In the left pane, click Change User Account Control Settings.

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The User Account Control Settings dialog box appears, as shown in the figure below.

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Slide the vertical bar (on the left side) to your desired setting and click OK.

There are four possible UAC settings, described as follows:

Always notify: This is the most secure option. It notifies you anytime a program tries to make changes to your computer or to Windows settings. When you are notified of a pending change, your desktop is dimmed (to prevent other programs from running until a decision is made), and you must either approve or deny the change in the UAC dialog box.

Notify me only when programs try to make changes to my computer: This is the default setting Windows notifies you anytime a program tries to make changes to your computer or if a program outside of Windows attempts to make changes to a Windows setting.

Notify me only when programs try to make changes to my computer (do not dim my desktop): Same as the previous setting, except the desktop is not dimmed, which may allow some malicious programs to alter the appearance of the dialog box.

Never notify: This is the least secure setting. If you're logged on as a standard user, changes that require administrator permissions will be denied. If you're logged in as an administrator, those changes will be automatically permitted, potentially exposing your computer, network, and personal information to security risks.

  • Attempt to install legacy (older) applications in compatibility mode. Select the older OS that the application was originally written for. It is less likely that updates or the latest service pack(SP) will help in this situation. Security updates probably won't have an effect on this scenario either.
  • The problems such as video card, network card, and modem card can be resolved by booting to Safe Mode. While in Safe Mode, troubleshoot the problem. In Safe Mode, you can uninstall the driver(s) that is causing problem with normal boot process.
  • If your PC is slow, check for excessive paging. The most likely cause for excessive paging is due to insufficient Memory. Increase the physical Memory on your computer.
  • Traditionally, workstations can have multiple operating systems installed on them but run only one at a time. By running virtualization software, the same workstation can be running Window 7 along with Windows Server 2008 and Red Hat Enterprise Linux (or almost any other operating system) at the same time, allowing a developer to test code in various environments as well as cut and paste between them within a virtual machine (VM).
  • If you are unable to remove a suspect file, boot in Safe Mode. In Safe Mode, only required services are loaded. It would typically be possible to remove the file in Safe Mode.

Email sending spam: If a user reports that several emails are being sent using his account without his knowledge. Actually, it might occur in two ways, 1) that the spammer has hijacked your email address, 2) that he spoofed your email address. First step in resolving the problem is to change the account password. This would eliminate that some one hijacking your email account. In the second case, the attacker doesn't have access to your email account, but using your email ID as "From" address to send spam. The IP address, host name etc. would be different.

There is actually, no simple solution to this problem One feature that may be useful is DKIM. DKIM short for DomainKeys Identified Mail, is an email authentication method designed to detect email spoofing. It is a way to sign and verify email messages at the message transfer agent (MTA) level using public and private keys. The public keys are published in DNS TXT records. DKIM authenticates the source and its contents.

Email spam (Receiving email): unsolicited mail is a big problem these days and there is no single solution to this problem. Sender Policy Framework (SPF) is an open standard specifying a technical method to prevent sender address forgery. SPF uses a DNS TXT record in the DNS zone file to limit the number of servers that are allowed to send email on behalf of a domain name. Basically, this is tells the receivers, "messages for my domain should only come from these servers." Messages that are coming from servers other than those specified in the SPF record will be viewed as spam and ignored. Below is an example of an SPF record for an example domain:

IN TXT "v=spf1 ip4:192.0.2.12 ip4:192.0.2.130 -all" This record tells us that the IPv4 addresses 192.0.2.1 and 192.0.2.129 are allowed to send email for the designated domain. With the use of "-all," we stress that only mail that matches this pattern of IPv4 addresses is allowed.

IsoPropyl Alcohol (IPA) is recommended for cleaning PCAs such as motherboards. Mild detergent can be used for cleaning the outside cabinet or the keyboard.

When attending to the computer maintenance or repair (other than the monitor), ensure that you work in a static free environment. Always wear wrist strap. You should not wear clothes/shoes that produce static charges. You should not use an Electrostatic Discharge (ESD) wrist strap when working on an open Cathode Ray Tube (CRT) display. An ESD wrist strap grounds your body to protect components from an ESD shock. However, a CRT display is highly charged, so you do not want to be grounded when you work inside one. In fact, only specially trained personnel should ever open a CRT display.

DLL stands for Dynamic Link Library. DLL is a special form of application code loaded into memory by request. A DLL is not executable by itself. More than one application may use the functions offered by a DLL.

Boot Options: The Advanced Boot Options menu lets you start Windows in advanced troubleshooting modes. The options available are

1. Repair your computer

2. Safe mode

3. Safe mode with networking

4. Safe mode with command prompt

5. Enable boot logging

6. Enable low resolution video (640 x 480)

7. Last Known Good Configuration (advanced)

8. Directory services restore mode

9. Debugging mode

10. Disable automatic restart on system failure

11. Disable Driver Signature Enforcement

12. Start Windows normally

NTLDR (New Technology Loader) Missing error:

If your Microsoft Windows 7-based computer does not start correctly or if it does not start at all, you can use the Windows Recovery Options to help you recover your system software. The causes for an error message like: 'NTLDR is Missing, Press any key to restart', may be due to any of the following reasons:

1. Computer is booting from a non-bootable source.

2. Computer hard disk drive is not properly setup in BIOS.

3. Corrupt NTLDR and/or NTDETECT.COM file.

4. Attempting to upgrade from a Windows 95, 98, or ME computer that is using FAT32.

5. Corrupt boot sector / master boot record.

6. Loose or Faulty IDE/EIDE hard disk drive cable.

To start recovery options

1. Insert the Windows 7 installation disc or USB flash drive, or a system repair disc, and then shut down your computer.

2. Restart your computer using the computer's power button.

Automated System Recovery (ASR) is a part of an overall plan for system recovery so that you are prepared if the system fails. ASR should be a last resort for system recovery. Use ASR only after you have exhausted other options. It is recommended that you use ASR only if all other options to repair the system (such as Last Known Good, and Safe Boot) have failed.

Steps to create Windows Automated System Recovery Disk on Windows 7 and Vista ASR

1. From the Start menu, select Control Panel.

2. Click Backup and Restore, and then on the left, choose Create a system repair disc.

3. Select a drive, and then click create

MSCONFIG: Short for "Microsoft System Configuration Utility" is designed to help you troubleshoot problems with your computer, MSCONFIG can also be used to ensure that your computer boots faster. Every time you boot your computer a lot of "hidden" programs load in the background. Some of these hidden programs are essential, but most aren't. Turning off some of these hidden programs (or services) can significantly increase your computer's performance and reliability.

For example, you want to disable DLP program from your computer from startup. To do so, you access MSconfig (System Configuration utility), and then the Services and Startup tabs in order to disable the two components of DLP 2.0 (DLP short for Data Loss Prevention).

1. The Startup tab will allow you to disable the actual application stored in Program Files, stopping the application from starting up when the user logs in.

2. The Services tab will allow you to disable the underlying service so that fewer resources are used, and there is less chance of system issues.

3. The General tab gives you several different startup selections.

4. The Boot tab allows you to modify how the system boots.

5. The Tools tab enables you to launch various OS utilities directly from Msconfig.

Event Logs: Event Log Explorer helps you to quickly browse, find and report on problems, security warnings and all other events that are generated within Windows.

Available logs in Windows 7 are:

1. Application (program) - Events are classified as error, warning, or information, depending on the severity of the event. An error is a significant problem, such as loss of data. A warning is an event that isn't necessarily significant, but might indicate a possible future problem. An information event describes the successful operation of a program, driver, or service.

2. Security - These events are called audits and are described as successful or failed depending on the event, such as whether a user trying to log on to Windows was successful.

3. Setup - Computers that are configured as domain controllers will have additional logs displayed here.

4. System - System events are logged by Windows and Windows system services, and are classified as error, warning, or information.

5. Forwarded Events - These events are forwarded to this log by other computers.

Some of the troubleshooting tools

1. Log files: A log file (or simply log) is a file that records either the events which happen while an operating system or other software runs. The act of keeping a logfile is called logging. When a failure occurs in Windows Setup, review the entires in the Setuperr.log file, then the Setupact.log file, and then other log files as appropriate.

2. Setuperr.log contains information about setup errors during the installation of Windows 7/Vista. Start with this log file when troubleshooting. A file size of 0 bytes indicates no errors during installation.

3. Setupact.log contains the events that occurred during the installation. There are several instances of the Setupact.log file, depending on what point in the installation process the failure occurs.

4. Unattend.xml is the answer file used by Windows 7/Vista during unattended installations.

5. Setuplog.txt records events that occurred during the text portion installation of Windows XP. Windows 7/Vista does not have a text portion during installation.

Process Kill: If you prefer to kill processes using the Command Prompt, you can do it. You have to run the Command Prompt as Administrator. To do this just right click command prompt from "All Programs > Accessories > Command Prompt" then select "Run as Administrator" on the pop-up menu.

On the Command Prompt, perform the following.

1. Type "task list" and press enter. It will show you a list of all the running processes.

2. Now you can End any particular process by executing the "Task kill" command. For

Example, to kill Chrome just type.

Task kill /IM chrome.exe /F

Where:

/IM - Kill by Image Name

/F - Kill the process forcefully.

Of course, you can also do this using Task Manager without going to the command prompt.

System recovery Options:

1. The Windows 7 /Vista recovery environment (WinRE) is also known as System recovery options and recovery console.

2. Windows 7's Recovery Environment enables users to perform a variety of system and data recovery tasks on a system that won't boot normally, including:

1. Fixing boot-level startup problems (Startup Repair)

2. Returning your system to a previous configuration (System Restore)

3. Recovering your computer with a previously-created system image (System Image Recovery)

4. Checking for defective memory (Windows Memory Diagnostic)

5. Running command-prompt programs (Command Prompt)

3. Advanced Boot Options is the menu that can be accessed by pressing F8, which is available in 7/Vista. It is also referred to as ABOM

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It is very important that you verify that the backup is working properly. It may so happen that you have several backup tapes, but none of them is good.

SFC: Sfc /scannow will inspect all of the important Windows files on your computer, including Windows DLL files. If System File Checker finds an issue with any of these protected files, it will replace it. You must be logged in as a user with administrator rights in order to run the sfc /scannow command.

Pressing F8 during boot process in Windows 7 desktop bring up the following options:

1. Safe Mode

2. Safe Mode with Networking

3. Safe Mode with Command Prompt

4. Enable Boot Logging

5. Enable Low-Resolution Video

6. Last Known Good Configuration (advanced)

7. Directory Services Restore Mode

8. Debugging Mode

9. Disable Automatic Restart on System Failure

10. Disable Driver Signature Enforcement

Driver Verifier is included in Windows 7, Windows Vista, and Windows Server 2003 to promote stability and reliability. You can use this tool to troubleshoot driver issues. You can start the tool by going to Run > verifier.exe

1. You can start verification of any driver without rebooting, even if Driver Verifier is not already running.

2. You can start the verification of a driver that is already loaded.

3. You can activate or deactivate most Driver Verifier options without rebooting.

PC Security Issues with appropriate tools

Traditionally, antivirus software relies upon signatures to identify malware. This can be very effective, but cannot defend against malware unless samples have already been obtained, signatures generated and updates distributed to users. Because of this, signature-based approaches are not effective against zero-day viruses.

A zero-day (or zero-hour or day zero) attack or threat is an attack that exploits a previously unknown vulnerability in a computer application, meaning that the attack occurs on "day zero" of awareness of the vulnerability. This means that the developers have had zero days to address and patch the vulnerability.

It is possible that sensitive information is relayed to the hacker unless the infected system is disconnected from the network. It may also infect other systems by remote triggering.

System Restore automatically track changes to your computer and creates restore points before major changes are to occur. To create a restore point, System Restore takes a full snapshot of the registry and some dynamic system files. For example, restore points are created before new device drivers, automatic updates, unsigned drivers, and some applications are installed.

To create a System Restore Point in Windows 7, use the sequence, Start | All Programs |Accessories | System Tools, and then click System Restore. Alternatively, you may just type "restore" in the search box, and click on the "System Restore" option that appears above.

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