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Google·Software Engineer·Technical Phone Screen·Senior

Senior
Apr 2026

Summary

Security engineer screen at Google, one technical question about Windows internals. Pretty focused session, no fluff.

Questions Asked (1)

Q1

How does malware achieve persistence on Windows machines?

System DesignTechnical Trade-offsRoot Cause Analysis
Author's notes

This is the kind of question where you can go wide or deep and it's genuinely hard to know which they want.

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AI HintsAI Generated

Suggested Approach

Start by defining persistence as a mechanism to survive reboots and user logoffs, then categorize the main techniques (registry, startup folders, scheduled tasks, services, WMI, etc.). For each category, explain how it works, why it's effective, and how defenders might detect it, emphasizing trade-offs like stealth vs. reliability.

Pro tip: Demonstrate depth by discussing how modern malware often uses fileless techniques and living-off-the-land binaries (LOLBins) to evade detection, and mention that understanding persistence is crucial for both offensive and defensive security.

1. Define persistence and its importance

Explain that persistence allows malware to remain active across system restarts, user logoffs, and other disruptions, ensuring continued access.

2. Categorize persistence mechanisms

Group techniques into categories such as registry modifications, startup folder, scheduled tasks, services, WMI event subscriptions, and bootkits.

3. Explain each category with examples

For each category, describe how it works (e.g., Run keys in registry, Task Scheduler, Windows services) and provide concrete examples of malware using them.

4. Discuss trade-offs and detection

Analyze the trade-offs between stealth, reliability, and complexity for each method, and mention how defenders can detect them (e.g., monitoring registry changes, service creation).

5. Conclude with modern trends

Summarize that attackers often combine multiple methods and increasingly use fileless techniques, emphasizing the need for layered defense.

Key Points to Mention

  • Registry Run keys (HKCU/HKLM) and startup folder
  • Scheduled tasks and Windows services
  • WMI event subscriptions and bootkits
  • Fileless persistence and LOLBins
  • Detection methods: Sysinternals Autoruns, Event Logs, EDR
  • Trade-offs: stealth vs. reliability vs. privilege requirements

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.