A zero-day attack 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
* Configuring AAA Services. Retrieved from https://www.cisco.com/c/en/us/td/docs/routers/crs/software
/crs_r4-0/security/configuration/guide/sc40crsbook_chapter1.html

Multifactor authentication (MFA) is a security measure that requires users to provide multiple pieces of evidence when logging in to an account or system. This can include a combination of something the user knows (e.g. a password or PIN), something the user has (e.g. a security token or smartphone) and something the user is (e.g. biometrics such as a fingerprint or face scan). By enabling MFA, the systems administrator can ensure that users are required to provide multiple pieces of evidence when logging in, making it more difficult for unauthorized users to gain access to the system. This can help reduce the number of help desk tickets submitted due to forgotten passwords.

The first thing that a support technician should check to resolve the issue of not being able to receive emails or browse the internet from a smartphone while traveling is the data plan coverage. The data plan coverage determines how much data and where the user can use on the smartphone's cellular network. The data plan coverage may vary depending on the user's location, carrier and subscription. The data plan coverage may not include or support certain areas or countries that the user is traveling to, or may charge extra fees or limit the speed or amount of data that the user can use. The data plan coverage does not affect text messages and phone calls, which use different network services and protocols. User account status is not likely to cause the issue of not being able to receive emails or browse the internet from a smartphone while traveling, unless the user account has been suspended or terminated by the carrier or the email provider. Mobile OS version is not likely to cause the issue of not being able to receive emails or browse the internet from a smartphone while traveling, unless the mobile OS has a major bug or compatibility problem with the network or the email app.
Network traffic outages may cause the issue of not being able to receive emails or browse the internet from a smartphone while traveling, but they are less likely and less common than data plan coverage issues, and they should also affect text messages and phone calls. References: CompTIA A+ Core 2 (220-1002) Certification Exam Objectives Version 4.0, Domain 1.5

Hash verification is a process that verifies the integrity of a file by comparing the hash value of the downloaded file to the hash value provided by the source1

Group Policy is a feature of Windows that allows administrators to centrally manage and configure the settings of computers and users in a domain network. Group Policy can be used to modify the default home page of all the workstations in a company by creating and applying a policy that specifies the desired URL for the home page. This way, the change will be automatically applied to all the workstations that are joined to the domain and receive the policy.