Earlier this month, security experts warned of a highly effective phishing email that fooled many Gmail customers into divulging their login credentials. Now, police say scammers are targeting our cell phones, too.
Con artists behind the scheme, which is being called the “Can you hear me?” scam, call potential victims and ask a simple question: Can you hear me? The goal is to get the person on the other end of the line to say the word “yes.” Police say scammers record the affirmative response in an effort to use the recording to authorize fraudulent and unwanted charges.
Related: Scams Even You Could Fall for (and How to Avoid Them)
Although criminals need more than a recorded “yes” to make purchases, they may already have access to credit card numbers and sensitive, identifying information that can be used to make charges. They can then use the recorded “yes” response in attempt to prove they gained your permission to make the charge.
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Though it may be tempting to answer calls from an unknown number—what if it’s someone you know who needs to reach you in a pinch?—the surest way to protect yourself is to let these types of calls go to voicemail. Anyone who needs to reach you will call back or leave a voicemail.
If you do decide to answer, always verify the caller and never give out personal information. (Though scammers may claim to be from a credit card company or a government agency, legitimate requests from these organizations will never be made over the phone.) You can also sign up for a service like Nomorobo, which analyzes your incoming calls and blocks any numbers with a high number of registered complaints.
Related: How to (Finally!) Stop Getting All Those Annoying Calls
If you suspect you may be victim of a scam like this one, check all bills—credit cards and utilities—thoroughly, and dispute any unrecognized charges immediately. If you discover unusual activity, you should also place a fraud alert on your credit file by contacting one of the credit reporting agencies.
This article originally appeared on RealSimple.com.