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Snooping With a Phone — Hot Tips from Private Investigators for Poking Into Secrets With Telephones

Updated on January 12, 2019
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Lyndon Henry is a writer, journalist, editor, and writing-editing consultant.


The U.S. government, state and local law enforcement authorities, and a handful of really mammoth mega-corporations routinely use subterfuge and technology to track us all (see my article Is Big Brother Watching? You Can Probably Count on It...).

So it seems only fair that humble, ordinary folks should learn a few tricks about snooping, too. And a good place to start is to look at the tools and tricks of private investigators (PIs), many of whom are masters at the art of poking and probing into areas others would like to keep secret.

In an increasingly dog-eat-dog world, you may need some of these tips just to protect yourself, and to survive.

By far one of the most commonplace but also valuable of these tools and tricks involves using the lowly telephone. So, how do PIs use the telephone effectively as a tool to gather info? Here are several of the hottest tips.

Most valuable tips

• Blocking Caller ID — PIs frequently need to make phonecalls anonymously, or under pretense with a fictitious name. If you're trying to pretend you're just a friend, the doctor's office, or whatever, you certainly don't want "Knowzee Detective Agency" displayed as the incoming caller.

In the USA, you can block Caller ID on a single call by dialing *67 just before the number (other countries may have similar codes). Also, for a fee, you can have all outgoing Caller ID blocked from the phone you're using.

However, keep in mind that, if the recipient subscribes to Caller ID, your call will probably appear as "Unknown Caller", "Blocked Call", "Anonymous", or some other cryptic label. It's probably a tad better than the detective service giveaway, but still, it's kind of suspicious. Also, some people pay for Anonymous Caller Rejection, and so your call won't get through to them at all.

There are alternatives that may work. For example, with some cellphone services, it's OK to call somebody via voicemail. You just wait to hear for a calling option, then you dial the number. Since they're routing your call through their voicemail system, it's basically being filtered through the voicemail service's line, automatically blocking your own phone number from being displayed.

Other services likewise filter your call through a third-party number, thus also blocking your number from being displayed. These include using pre-paid phone cards, or, from your own computer, calling via a voice-over-IP (VoIP) system like Skype.

• Spoofing Caller ID — Even better, if you can do it, for disguising your real identify is spoofing the number of the phone you're calling from.

This means duping the phone system into displaying a Caller ID number to the recipient that's essentially phony — i.e., not the real one of the actual originating phone. Wikipedia has a good overview on this you might want to check out — see Caller ID spoofing.

As a general rule, Caller ID spoofing isn't (yet) illegal in the USA. However, the Caller ID Act of 2009 made it a crime to do this for the purpose of causing harm or defrauding the person you're calling.

Caller ID can be spoofed through a variety of different methods and technologies. It used to be pretty expensive, requiring a fairly advanced knowledge of phone technology. But with the availability of new software approaches — especially open-source software like FreeSWITCH and Asterisk, or various VoIP services, Caller ID spoofing has been made affordable and easy for just about anyone.

In recent years, various commercial spoofing services have become available — for example, Caller ID spoofing services that allow customers to initiate number-spoofed calls from an Internet-based interface (PC, smartphone, etc.).

In fact, there are literally dozens of Caller ID spoofing companies that have sprung up to meet the mushrooming demand for this kind of deception. Certainly, one of the oldest, largest, and most popular is SpoofCard, which, like similar services, basically works sort of like a regular phone calling card. Stealth Card and Bluff My Call are other similar major spoofing services.

(Incidentally, Caller ID spoofing, in the wrong hands, could be a little like the "phishing" deception used by Internet scammers trying to dupe you into providing crucial personal information. So be careful — that incoming call may not actually be coming from where it otherwise seems — and if you're asked to divulge sensitive information, you might prefer to call the company back directly, so you have real, verifiable control over whom you're speaking with.)

• Special phone line — Another clever technique used by PIs is to install a separate unlisted phone line in their office, mainly to receive calls under various pretexts. For example, they might provide this number when they're using a pseudonym or some kind of pretext in one of their investigations. Or perhaps they just want a way to avoid divulging who they actually are, and to remain anonymous. This line is unpublished, and always answered with something nondescript, such as "Business Office".

• Recording calls — Really savvy PIs use a completely self-contained long-play recorder for logging both incoming and outgoing numbers dialed. A separate decoder may be required for this device to decode the dialed numbers; some models can decode calls when the recording is played back.

Sources such as provide a wide range of digital voice and phone recorder devices as well as phone recording software.

• Cellphone recording — Depending on the phone, it may seem like a big problem to record calls on your cellphone. However, there are fairly easy and affordable solutions, mainly involving using compact recorders with hands-free microphones. A useful assortment of these and similar devices can be found on the Web — one example is the Spy Exchange & Security Center.

• Detecting lies — OK, you're managed to get your "subject" (the one you've got under surveillance) to speak with you, but is there a way to tell if he or she's being honest? Sure — your computer can become a live lie detector when you're on the phone. Voice verification software is available to perform live analysis, or after-the-fact from a recorded conversation.

For example, X13-VSA promises that "Now You Can Turn Your Computer or Laptop Into A Truth Verification Device". This, they claim, functions as a "Fully computerized voice stress analyzer that allows you to detect the truth".

• Cellphone carrier — How can you figure out which cellphone carrier your subject is using for his or her phone? Try this trick PIs use: Just call that cell number when you know the phone's turned off. Almost always, there'll be a recorded message about the number "not being available at this time" ... plus the message will usually name the carrier, so voilà!

• Tracing an old cell number — How do PIs figure out who an old cellphone number belonged to? One way is to contact the cellphone service, claim you're interested in using that number, but you'd like to know who had the number previously. Usually the carrier will look it up for you and give you that information.

• Voice alteration — Occasions arise when a PI needs to effectively disguise his or her voice. For example, you've represented yourself in one role to someone, but you suddenly find a need to represent yourself in a different role. Fortunately for PIs, nowadays there are quite a number of different types of affordable and reliable electronic voice changers, including portable devices. A number of these are described and reviewed online — see Telephone Voice Changers.

Summing up

Certainly, the information provided in this list doesn't exhaustively cover all the possible telephone procedures and techniques used by professional PIs ... but they're definitely some of the hottest and most useful tips. And hopefully, in a world increasingly permeated by top-level surveillance, spying, and manipulation, disseminating information like this will represent a small step toward trying to level the playing field — at least a little bit.


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    • Vicki Goldsberry profile image

      Vicki Goldsberry 

      6 years ago from Texas



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