System designers have long struggled with the challenge of determining how to control when untrusted applica- tions may perform operations using privacy-sensitive sen- sors securely and effectively. Current systems request that users authorize such operations once (i.e., on install or first use), but malicious applications may abuse such authorizations to collect data stealthily using such sensors. Proposed research methods enable systems to infer the op- erations associated with user input events, but malicious applications may still trick users into allowing unexpected, stealthy operations. To prevent users from being tricked, we propose to bind applications’ operation requests to the associated user input events and how they were ob- tained explicitly, enabling users to authorize operations on privacy-sensitive sensors unambiguously and reuse such authorizations.
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