Objective 3.3
220-1202Given a scenario, troubleshoot common mobile OS and application security issues.
Objective 3.3 sits in Software Troubleshooting, which carries 23% of the A+ Core 2 exam. The questions below are original, written from the official objective title above, and each explanation cites the CompTIA page it rests on.
Objective title verbatim from the official objectives. CompTIA exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
A vendor emails a technician an APK for an in-house Android app. The package installer refuses to proceed and reports that the file is not signed. What must happen before this app can install?
Correct.
Checked against source.android.com, August 2026Concept
Android uses a package's digital signature to answer who produced it and whether the bytes have been altered since. A package carrying no certificate answers neither question, so the platform has no basis on which to admit it.
Why B
The installer reads the certificate carried inside the package as its first check. A file that carries none is turned away by the on-device installer and by the store alike, whoever handed the file over and whatever it claims to be.
Source
Android Open Source Project: App signing, checked August 2026Every app that is run on the Android platform must be signed by the developer. Apps that attempt to install without being signed are rejected by either Google Play or the package installer on the Android device.
Now you: objective 3.3 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
A user sideloaded what a website called a newer build of an app already installed on their Android phone. The install stops, yet the same file installs cleanly on a phone without that app. What explains this?
Sample question 2 of 3
A user says an app they installed from a link outside the store stopped working overnight. Its icon is still on the home screen, tapping it does nothing, and nobody uninstalled anything. What happened?
Sample question 3 of 3
A user manually installed a certificate profile that the security team emailed, and Settings shows the profile as installed. The internal HTTPS site still reports an untrusted certificate. What step is missing?
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Read the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.