A cybersecurity expert has developed a tool that can exploit a vulnerability in WhatsApp and Signal, potentially putting over 3 billion users worldwide at risk. The tool, dubbed “Silent Whisper,” allows attackers to monitor a user’s activity using just their phone number—without sending a message or alerting the user.
How the Attack Works
According to cybersecurity reports, both WhatsApp and Signal automatically send delivery confirmations when a message arrives. These confirmations happen so quickly that users do not notice them. Attackers can track the timing of these confirmations to determine whether a phone is on or off, if the user is actively using it, or even their location. Over time, this can reveal daily routines, sleeping and waking patterns, and travel habits—all without reading messages or accessing the contact list.
Warning Signs of the Attack
Users may notice unusually rapid battery drain. Under normal use, a phone loses less than 1% battery per hour when idle. During this attack, devices like iPhone 13 Pro, iPhone 11, and Samsung Galaxy S23 have shown battery losses of 14–18% per hour. Mobile data consumption also rises significantly, causing issues with calls or video streaming, while the phone may feel unusually warm.
Can You Protect Yourself?
Turning off read receipts may reduce exposure but does not fully protect users. WhatsApp and Signal have yet to patch this vulnerability as of December 2025. Limiting messages from unknown numbers may help, but its effectiveness is unclear.
The developer emphasized that the tool was created for research purposes only, yet it can be misused if downloaded and operated by malicious actors. Users are advised to remain vigilant and monitor unusual phone activity.
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