System File Checker to check for modified Windows files. System File Checker (SFC) is a Windows utility that can be used to scan for and restore corrupt Windows system files. SFC can be used to detect and fix any modified or corrupted system files on a computer, and thus should be checked first when a user reports that their computer has been running slowly since the installation of security applications [1][2]. By checking SFC, any modified or corrupted system files can be identified and fixed, potentially improving the overall performance of the computer.

A possible cause of the user being redirected to unexpected websites is that the localhost file entries have been modified by malware or hackers to point to malicious or unwanted websites. The localhost file is a text file that maps hostnames to IP addresses and can override DNS settings. By examining the localhost file entries, a technician can identify and remove any suspicious or unauthorized entries that may cause the redirection issue. Enabling firewall ACLs may not resolve the issue if the firewall rules do not block the malicious or unwanted websites. Verifying the routing tables may not resolve the issue if the routing configuration is correct and does not affect the web traffic. Updating the antivirus definitions may help prevent future infections but may not remove the existing malware or changes to the localhost file. References: CompTIA A+ Core 2 (220-1002) Certification Exam Objectives Version 4.0, Domain 1.3

Malware is malicious software that can cause damage or harm to a computer system or network4. A technician has verified a computer is infected with malware by observing unusual behavior, such as slow performance, pop-ups, or unwanted ads. The technician isolates the system and updates the anti-malware software to prevent further infection or spread of the malware. The next step is to run repeated remediation scans until the malware is removed. A remediation scan is a scan that detects and removes malware from the system. Running one scan may not be enough to remove all traces of malware, as some malware may hide or regenerate itself.

For updating software on several hundred Mac laptops, the best method is Mobile Device Management (MDM). MDM solutions allow administrators to remotely manage and update software across multiple devices efficiently, making it an ideal choice for handling software updates on a large scale.

The correct answers are D. Restricting log-in times and E. Enabling a screen lock. These are the security measures that can be used to prevent the computers from being accessed by unsupervised contractors in the building.
* Restricting log-in times means setting a policy that allows users to log in only during certain hours, such as the regular working hours of the company. This will prevent unauthorized access by contractors who work at night1.
* Enabling a screen lock means setting a policy that requires users to enter a password or a PIN to unlock their screens after a period of inactivity. This will prevent unauthorized access by contractors who might try to use the computers when the users are away2.
1: CompTIA A+ Certification Exam: Core 2 Objectives, page 19, section 2.3. 2: CompTIA A+ Certification Exam: Core 2 Objectives, page 20, section 2.4.