Detecting and Measuring Fake Accounts
Scenario
Facebook wants to understand and curb fake-account activity both over the past month and at sign-up time.
Tasks
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Month-over-month proxies: List product or engagement metrics that could indicate changes in fake-account activity.
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Post-registration signals: Identify behavioral signals that help distinguish fake from real accounts after signup.
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Registration-time detection: Can we flag a fake account during the registration flow? Propose features and quick checks.
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Bayesian update: Given a prior fake-account rate of 2% and observing 18 flags in a cohort of 600 new accounts, compute the posterior probability that the next account is fake. Use Beta–Binomial conjugacy and show steps.
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Classifier objective: For evaluating a fake-account classifier, would you optimize precision or recall? Discuss the trade-offs and wider impact on Facebook.