A horrified woman looking at her smartphone.

Robocalls—the digital equivalent of mosquitoes in your bedroom on a hot summer evening—aren’t just annoying, they’re potentially dangerous. These automated phone calls can put you at risk of falling for scams that can have devastating financial consequences.

In July alone, more than 4 billion robocalls were made in the U.S., up from 2.6 billion one year ago, estimates YouMail, a provider of voicemail and call-blocking services. While some were legitimate, such as calls to your home phone for debt collection and reminders about doctor’s appointments, many came from fraudsters trying to trick you out of your money.  

More On Robocalls

Even more confounding to many people is that the calls are sometimes in different languages. The Federal Trade Commission, which helps consumers and law enforcement collect information on illegal phone calls, recently warned about scams from robocallers in Chinese. The callers ask for your bank or credit card information or tell you to make a bank transfer to them.

These and other telemarketing scams cost consumers hundreds of millions of dollars, says Maureen Mahoney, a policy analyst for Consumers Union, the advocacy division of Consumer Reports. “Vulnerable consumers such as the elderly may be unduly susceptible to telemarketing pitches for products that they do not want or need,” she says.

While telephone carriers, third-party companies, and robocall experts have long offered tools to help mitigate the calls, some new systems are being created.

One, known as Shaken and Stirred, is being developed by a number of companies in the telecom industry. It is essentially an authentication system that sniffs out incoming calls to ensure that they are legitimate. The system works by verifying that a call being made is identified accurately when it reaches your carrier and before it gets to your phone, says Paul Florack, vice president of Transaction Network Services, a provider of telecommunications services based in Reston, Va. With such a system, carriers would be able to prevent spoofing, a tactic robocallers use that makes a bogus name or phone number appear on your caller ID screen, fooling you into answering.

While this technology promises to help prevent robocalls, it is still a few years away from being implemented, Florack says. Carriers need to agree to use the system, and it could cost them tens of millions of dollars each to roll out.

How to Avoid Robocalls

For now, there are precautions you can take to minimize the number of robocalls you receive.

List Your Phone Number With the Do Not Call Registry
By signing up for the Do Not Call Registry, you can request that your landline or cellular phone number be removed from the call lists companies use. That should help reduce the number of calls you get from legitimate telemarketers and robocallers.

What you should know: You’ll still get calls from organizations with which you have established a business relationship; calls for which you have given prior written permission; calls that are not commercial or do not include unsolicited advertisements, such as school closings, tornado warnings, and other civic notices; and calls by or on behalf of tax-exempt nonprofit organizations, which include political solicitations.

And you should realize that many dishonest robocallers ignore the laws and will call you anyway.

Sign Up for Your Carrier’s Robocall Alert Service
Many companies, including Verizon, AT&T, T-Mobile, Sprint, and U.S. Cellular, have introduced services that alert you that an incoming robocall may be from a scammer or spammer. In some cases, such services are free, but for a few dollars more per month you can get a more robust version that can block the robocalls from ringing on your phone.

AT&T, for example, offers a basic free service that customers must enable in order to use. But for $4 per month it offers Call Protect Plus, which the company says is more robust and includes automatic fraud blocking. Verizon offers a screening service called Premium Caller ID for $3 per month. T-Mobile offers a service for no additional charge.

What you should know: According to a recent study by Mind Commerce, a research company that specializes in phone systems and networking technology, the carriers’ systems are able to successfully notify customers of calls that may be problematic. Verizon’s service did the best job, according to the report, succeeding 93 percent of the time. T-Mobile’s service accurately alerted its customers to suspicious calls 90 percent of the time, while AT&T’s service was accurate 86 percent of the time. Sprint and U.S. Cellular have systems similar to Verizon’s, so they were excluded from the study.

Download a Call-Blocking App
Instead of simply being alerted to incoming robocalls, a call-blocking app can intercept robocalls before they reach you, says Mahoney of Consumers Union. Among the providers are Nomorobo, which charges $2 per month for its service (there is no cost for landlines), and free apps such as Hiya, Mr. Number, RoboKiller, and YouMail.

What you should know: While some apps, like Nomorobo, don’t access your contact lists, some of the free apps do, Florack says. If you’re planning to download a robo-blocking app, read the app’s privacy policy first.

Reject Anonymous Calls
Another option available from some phone companies, phones, and call-blocking equipment is to automatically reject anonymous calls. If you turn this feature on, all anonymous calls are instantly rejected, preventing the caller from even leaving a message.

What you should know: The downside is that this may prevent you from receiving legitimate calls from friends, relatives, or others who, for privacy reasons, don’t want their number and other information showing up on caller ID.

If you receive an unwanted call that you believe is spam or a scam, make sure to report it to the FTC. You can make a report online here. By reporting unwanted calls, you can help the regulator go after bad actors.