Safety researchers have uncovered a vital privateness flaw dubbed “Careless Whisper” that lets attackers monitor consumer exercise on WhatsApp and Sign by silent supply receipts, with out alerting victims or needing prior contact.
By crafting stealthy messages like reactions to nonexistent content material or timed-out edits, adversaries set off round-trip time (RTT) responses revealing machine states, all exploitable with only a telephone quantity.
This impacts over three billion WhatsApp customers and tens of millions on Sign, enabling routine monitoring or battery drain.
Attackers ship invisible actions, self-reactions, response removals, or invalid deletions that immediate particular person supply receipts from every goal machine, even with out ongoing chats.
These receipts expose RTT variations: roughly one second for screen-on states, two seconds when off, and 300 milliseconds if the app runs in foreground on iPhones.
Excessive-frequency pings, as much as sub-second on WhatsApp, amplify precision with out notifications, not like prior overt strategies, that are restricted by alerts.
Multi-device setups worsen leakage, as companion purchasers (net, desktop) reply individually, making it tougher to detect on-line standing shifts like desktop boot-ups signaling workplace arrival, reads the report.
In real-world exams, researchers tracked a Xiaomi telephone’s Wi-Fi/LTE switches, calls, and laptop computer syncs throughout networks.
MessengerStealthy from StrangerMulti-Gadget ProbingThreema ComparisonWhatsAppYesIndependent receiptsRestrictive, single receiptSignalYesIndependent receiptsNo spooky stranger probingThreemaNoSynchronized receiptsN/A
RTT patterns fingerprint OSes by way of receipt ordering, separate on Android/iOS WhatsApp, stacked reversed on macOS, whereas jitter distinguishes chipsets like Qualcomm versus Exynos.
Gadget fashions
Attackers infer schedules, display screen time, or app utilization, escalating from country-level geolocation in previous work to second-granularity conduct.
Offensively, outsized reactions (1MB payloads) drive 3.7MB/second site visitors, 13GB/hour silently inflating knowledge payments or draining batteries 14-18% hourly on iPhones/Samsungs. No charge limits curb sustained blasts.
Reported September 2024, Meta confirmed triage however issued no patch after 14 months; Sign ignored findings.
Researchers urge proscribing receipts to contacts, including RTT noise, consumer validation of message IDs, and server charge limits. Customers can restrict unknown messages in privateness settings as an interim protection.
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