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Devices for covert surveillance

3 April 2015, by — admin ()

Technology and the human imagination do not stand still. This results in us having, not only modern computers, smart phones, and other consumer devices, but also a huge selection of modern high-tech devices, which are not known to the majority of consumers.

The focus is on hardware devices that are designed to collect (sometimes tacitly), store and transmit information (voice recorders, bugs, hidden cameras), as well as on devices that are designed to protect against such interception (suppressors, detectors).

The aim of the article is not to promote the use of such technology (let’s leave this to special services and detectives), but to inform people about how they can be monitored and how they can protect themselves from spy devices.

The most interesting spy devices

Voice recorders

There is a variety of reasons why voice recorders have always been some of the most popular spy devices.

After all, it is much easier to record sound than it is to record video — there is no need to keep the device in sight. This is a very simple device — a microphone, a memory card, a battery, and a very simple circuit – there are no expensive components or complex technical solutions. Voice recorders are not sensitive to many signal jammers (they can, however, be affected by noise generators).
Voice recorders are also popular among journalists and students for note-taking.

Their disadvantages are obvious:

  • Their batteries and memory cards have limited capacity.
  • You need install and to remove the device after the recording has finished.
  • An audio recording does not provide an accurate understanding of what is happening.
  • Thorough field detector work will detect the device.

There is a separate class of voice recorders that are installed in the gap between telephone lines, but they are losing their relevance right alongside the phone lines.
Voice recorders can be made in the form of a conventional recorder (sometimes even with a massive and sensitive external microphone), and in the form of consumer devices (remote controls, flash drives, pens).

Please note: voice recorders that are disguised as everyday objects are illegal in some countries (e.g. Russia) and their acquisition may lead to criminal prosecution.

Audio bugs

Functionally, the difference between these devices and voice recorders is that audio bugs do not record sound but pass it along.

The simplest bugs are primitive radio transmitters. A signal that they broadcast can be heard through the common household radio when set to a given range.

The more advanced models encrypt the signals. To receive it, you need a receiving device that is included in the bug kit.

Most modern bugs work by GSM protocol (mobile communication) and to obtain a signal with them, you need a cell phone (which, in turn, needs a SIM-card of a local mobile operator).
Some bugs work from their own power supply, and some can be connected to some electric home appliance or electric network.

They are not usually disguised as household items as they themselves have a very tiny size. Although, there are some devices that are disguised, for example as surge protectors, computer mice, ashtrays, etc.

The disadvantages of such products include:

  • They can be jammed by practically any Signal Jammer.
  • They can be detected by virtually any field detector.
  • They are illegal in many countries and available only to law enforcement agencies.



Microphones are not spy devices, per se, and generally are not regulated by any legislations. At the same time, a professional directional microphone that is connected to a conventional recorder is capable of recording the voice of a man who’s talking a few hundred meters from the device quite legibly.
It is simply impossible to hear this with a naked ear.
The disadvantages of such devices include the following:

  • They need to be in the line of sight of the sound source, with no sound-reflecting obstacles positioned between the sound source and the microphone;
  • There shouldn’t be strong sound sources close to the microphone;
  • These microphones obviously attract the attention of strangers.



Different types of video recorders include a great range of different devices.

This includes compact videocameras, action-cameras, dashboard cameras, video door entry systems, peephole cameras, and a variety of indoor and outdoor surveillance cameras with a variety of accessory equipment.

The use of the majority of these devices is legal, with the exception ofthe cameras camouflaged as everyday objects, cameras with a split type lens (a pin-hole), cameras with the ability to record inultra-low light conditions and cameras transmitting a signal elsewhere. In Russia, this prohibition applies primarily to an import and export of such devices across the border.

In recent years, the popularity of 3G-cameras has increased. Theyincludea SIM-card and the only thing you need isasmartphoneapplicationto view images from these cameras. For locations with access to the Internet, there are also IP and Wi-Fi cameras.


Dashboard cameras fall into a separate category of recording devices. All attempts to restrict and prohibit the use of these devices have failed and now they are widely used as an evidence of innocence fora person involved in a car accident, and a way of protecting oneself from illegal actions of the traffic police.

The class of cameras with lenses installed on a flexible endoscope is not in great favor because of its peculiarities. They are used mainly for operation in hard-to-reach spaces – inthe process of wiring, vehicle repair, etc.

Nowadays, compact cameras can be found anywhere — from reasonable places like motorcycle and bicycle helmets to absolutely crazy ones, such as eyes of a teddy bear, wrist watch dial or a belt buckle. The minuscule dimensions of the modern cameras can even allow them to be disguised as screws (the onesusedwithstandardcross-point screwdrivers).

As far as we know, defence and law enforcement agencies still prefer to disguise hidden cameras as buttons and items of clothing.

Their main drawback is the need to direct a shiny camera lens to an object of recording, which can be easily noticeable.

Signal suppressors influence only the cameras that transmit a signal. If a camera records a signal in its own memory, then they are unable to influence it.

Field detectors are also ineffective against cameras. There is a separate class of LED detectors targeted at hidden cameras lenses, but you should have certain skills to be able to work with them.


Modulators and voice encoders

Voice modulators change characteristics of the voice in real time, allowing a person to change his voice beyond recognition, for example, when talking on the phone.

Cheap devices are usually executed in the form of a handset cover or hands-free headset, which enables to change a voice only according to one of the standard built-in filters (for example, imitate a voice of a young girl or an old man).

Professional modulators are separate devices, that allow changing a voice in a way that neither human nor special equipment will be able to identify it.

Voice encoders are paired devices for confidential conversations on the phone. For example, if one of the phones is being tapped.

With the introduction of Android for mobile phones, these devices (both modulators and encoders) began to lose their relevance rapidly, since their functions can easily be performed by software application.



Hardware keyloggers (keyloggers) are small devices connected between a computer and a keyboard, which are able to store information about pressed keys.


More advanced versions of these devices can be connected to Wi-Fi networks and send all the collected information to an e-mail address of the owner.

There are versions for both PS\2 keyboards and for USB keyboards.

It is also possible to install these devices onto laptops, but the process is more complicated, because it requires a partial disassembly of the laptop.

These devices can be detected only with “one’s own eyes”, while suppressors and detectors are almost entirely powerless against them.

Of course, there are software versions of keyloggers and their functionality is much greater than that of their hardware counterparts.


Devices for protection from spying equipment

Usually these devices are manufactured and sold by the same companies that are engaged in production and selling of spying equipment. The only difference is that these devices are intended to protect people.

Suppressors of signals and recording devices

There are a lot of devices, the main purpose of which is to protect against eavesdropping (both in terms of audio and video).

One of the possible principles of their operation is creation of a more powerful signal that interrupts the spying equipment signal. Data transmission over radio channels, as well as geolocation systems and cellular communication, don’t work in the area where such devices operate.

It is worth noting that their effectiveness is not too high. For example, they don’t interfere with the operation of voice recorders and cameras, which save the videos into their memory.

Besides their obvious use for protection against eavesdropping, there is also an illegal method — criminals use to them to block the car anti-theft system.

Another interesting way to use them: signal suppressors are often used in conference rooms, theaters and concert halls to stop mobile phones from disrupting the order.

Alternative options of protection against eavesdropping include noise generators. They create a lot of noise in the range that cannot be perceived by the human ear, but (while the noise generator is operating) it disables all known types of microphones.

There are entire systems for acoustic and vibro-acoustic protection of spaces. These systems create vibrations of the elements in the space itself and disguise even speech sounds coming from directional laser microphones.

Field and camera detectors

These devices are used to check people and places for the presence of spying equipment. They operate on the principle of searching for the signal over a wide range.

In order to perform a complete check, all electrical equipment in the room, cell phones, and anything that can generate an electromagnetic field should first be turned off.

Detectors use sound, vibration or flashing LEDs to notify about detection of the signal.


A lot of field detectors come in combination with camera detector in the same housing. The principle of this detector operation is that the camera lens (even a split pin-hole) always reflects the light in a certain way. Using LEDs, the device creates a light flux, monitoring the room through which you can see the bright reflecting dots of camera lenses.

There also exist digital detectors of imaging cameras. They search for the video signal over the most popular frequencies and connect to them, if they find it. It is possible to find a camera location using an obtained image.


GPS-beacons and bugs

GPS-beacons are used for objects geolocation and transmission of the location data to the owner. Usually, they are guided by the GPS satellite signal and transmit the data signal via GSM. They are mostly compact devices, which are about the size of a matchbox.

They are used, for example, to protect auto and moto vehicles against theft, to control finding of an auto park vehicle or members of the staff.

There are many software equivalents for smartphones (GPS, Wi-Fi), as well as special services offered by cell-phone operators for geolocation of mobile phones (usually – triangulation and rarely GPS and Wi-Fi).

Bugs are different from the beacons in that they transmit geolocation data only upon the owner’s request, rather than continuously. This protects them from field detectors.

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