• Thermal Imaging
  • Near-Infrared Imaging
  • Night Vision
  • Video Surveillance
  • Thermal Imaging

  • Profile:


  • Thermal imaging systems sense long-wave infrared radiation (heat) and convert it to a video temperature-map. Originally designed for military applications ('vampire' sniper scopes), thermal imaging systems have become progressively cheaper and more accessible. Thermal imaging offers several key advantage over night vision systems; thermal imagers require no ambient light to operate (hence require no illuminator) and are unaffected by bright-light (thermal imagers won't bloom).


    A popular misconception about thermal imaging is that it will only pick up objects that radiate heat such as people. Everything above absolute zero emits infrared radiation, though hot objects emit more.


    Infrared cameras come in two varieties, 'cooled' and 'uncooled'. Cooled thermography systems contain their own cryogenic cooling systems which take their temperature down around -320 degrees F, making them extremely sensitive (.1 degrees C at 1000 feet). Despite their sensitivity and accuracy cooled IR cameras remain rare due to their cost. Uncooled IR cameras trade sensitivity for expense, instantaneous startup time and quieter operation. Uncooled thermography systems run at room temperature.


    Thermal imaging suffers from several drawbacks; they cannot distinguish fine details, and their penetration is poor. While an image intensifying system could pick out facial features or fine details IR scopes show only shilouetes. Thermal images are degraded by insulation, so they penetrate exterior walls and windows poorly.


    From a countermeasures prospective thermography offers several useful tools. Material density testing can be accomplished by examining a substance's thermal signature. Differences in heat and moisture caused by alternating densities can be reliably used to test for anomolies is a particular surface, allowing for non-destructive testing of walls. Surveillance devices will sometimes present a thermal signature in an area (a hotspot in a wall for instance).



  • Detection:


  • Cooled thermography systems present a sharp thermal signature.



  • Countermeasures:


  • Thermal imaging is primarily a threat in open areas. Protecting enclosed spaces from thermal imaging is a mater of insulation. Standard household insulation, in conjunction with double or triple glazed windows should render most thermal imaging useless by absorbing or reflecting long-wave (thermal) infrared.



  • Further Resources:


  • Infrared.com offers a law enforcement and surveillance specific tutorial on thermography



    Near-Infrared Imaging


  • Profile:


  • Near-infrared imaging is the use of imaging equipment sensitive to the near-infrared band (infrared light close to visible light). Unlike thermal imaging, near-IR does not sense heat, but instead is sensitive to infrared close to the visual spectrum. Because near-IR imaging equipment is sensitive to near-infrared light, it permits the use of (invisible) infrared illuminators.



    Sony incorporates NIR into some of their camcorders under the trademark Nightshot.



  • Detection:


  • Near infrared cameras require an IR illuminator to provide a light source. Viewing the area through the camera with all white light turned off and blocked out will show an IR 'bloom' from the illuminator. Care must be taken with infrared cameras to make sure that the searching camera's illuminator is either removed, turned off off or covered in order to prevent the illumiator's infrared light from overwhelming the IR generated by a transmitter. Many infrared video cameras have their illuminator on the front.


    Night vision devices can also be used to detect IR illuminator (be very careful and use a 99% filter or you risk frying your tubes and retinas), as can IR sensitive plastics (which are sold as testers for remote controls).



  • Countermeasures


  • Once a camera has been located, it can be rendered useless by directing a source of strong IR at it.



    Night Vision

  • Profile:


  • Night vision is an imaging technique that allows a user to see in extreme low light situations through the use of light-amplifying equipment. Night vision, once the tool of law enforcement and the military, is becoming progressively more accessible and less expensive as former eastern-bloc nations sell off their military hardware.


    Night vision equipment is divided in 'generations' based on the technology they use. Generation 0 is not generally considered night vision, but is instead an image conversion technology that uses IR illumination. Generation I was the first night vision system to be considered 'passive' (not explicitly requiring an external illuminator) First generation night vision systems use grid electrodes which accelerate electrons through an image intensifier tube. Generation I night vision is hamstrung by the optical problems of blooming (a sharp loss of contrast) and image distortion, as well as weight. Generations II and III utilize microchannel plates to amplify existing light, which correct the problems of distorted images and lower the weight considerably.


    Night vision amplifies existing light, so no night vision system will operate in total darkness. Should there be insufficient light an external light source will be needed. Different models of night vision equipment is sensitive to different wavelengths of light, with some systems more sensitive in the visible light spectrum and others in the infrared. This particular sensitivity defines what sort of illuminator must be used. Naturally, infrared sensitive systems allow for the use of an infrared illuminator which is invisible to the un-aided eye. Night vision illuminators may be external or built into the system (IR LEDs).



  • Detection:


  • Night vision is a 'passive' technology, meaning that it generates very little in the way of signals for a sweeper to find. Detecting night vision would more likely rely on either detecting the optics that it supplements, or by detecting its illuminator. Visible light illuminators will likely be rather difficult to see without some soft of imaging hardware of your own. Infrared illuminators can be detected as per infrared transmitters.



  • Countermeasures:


  • Almost all NVDs offer a feature known as automatic brightness control (ABC). ABC filters sources of bright light in order to preserve the tubes, and the eyes of the operator, both of which would be destroyed by a flash of bright light through an NVD. ABC can be exploited by illuminating the night vision system with a source of white light. Night vision without ABC will be damaged or destroyed by prolonged exposure to bright light.



    Video Surveillance

  • Profile:


  • Video surveillance is one of the most common types of surveillance. Law enforcement utilizes myriad covert video cameras, cameras sit atop traffic lights, and porno sites claim to have them secreted away in bathrooms across the globe. Covert video will most likely only become more common because of cameras and video transmitter ever decreaing cost and size (the one displayed below is actual size) and their growing availability (the classified ads in any electronics magazine will have a minimum six offers of surveillance cameras for sale).


    Video surveillance systems can be broken down into two distinct elements: the camera and the transmission system. Cameras can range in complexity from family camcorders to incredibly small light-amplifying CCD devices.


    Many 'spy cameras' will use a technology called CCD (charged coupled device). CCDs allow for very small cameras that give off much less heat than older tube models, and offer better preformance in low-light settings. CCD cameras sometimes incorporate infrared sensitivity.


    Video transmission systems fall into one of two categories; wired and wireless:


    Wired cameras are connected via a cable to a monitor or VCR where the video is viewed and/or recorded. Wired cameras are typically hampered by the need for wiring, though a clever eavesdropper could exploit the existing coaxial cable in an area by laying his cable parallel to the legitimate one. Range is less of an issue for wired surveillance cameras, though depending on the cables in use, a repeater might be nesecary.


    Wireless video cameras are becoming less expensive and smaller every day. While spy-store cameras have been available for quite some time, RF Link's inexpensive Wavecom wireless video transmitter best underscores how common they have become. Most wireless video cameras operate in the microwave range (due to the phenomenal bandwidth that video requires.


    Most wireless video systems operate on the unregulated 2.4 GHz band, although certain devices show up on the 5.8 GHz band.


    A relatively recent possibility for surveillance cameras is the use of a small camera connected to a networked computer, which would display the video over a network link. Such an arangement would allow an eavesdropper to monitor a location from anywhere in the world. A particularly alarming breed of network camera is the camera server, which incorporates a camera, server and networking hardware into a single package.


    Networked cameras also open computer users up to native threats through control suite programs.



    Do you have something like this sitting on your desk right now? It could be monitoring your activities.
    A covert surveillance camera.


  • Detection:


  • Detection of video cameras can be located by one of several methods. According to James Atkinson, video transmitters can be located by turning off the lights in a specfic area and running a 60-100 watt strobe and searching the bands with a receiver. The camera will generate bursts of raster buzz in sync with the strobes flashing, which can be detected on the receiver.


    Video devices can also be detected by picking off their transmission media (RF, wireline, etc). This tactic can fall short in a number of ways, however. Wireless video transmitters almost always utilize spread spectrum in order to get the required bandwqidth. This also spreads the signal out beyond where many receivers can pick it up. Covert Wavecom wireless video systems can be detected by using a Wavecom receiver with a good antenna. Set the receiver to channel 'A' and sweep the receiver against all surfaces. Repeat this procedure with the receiver on channel 'B', 'C' and 'D'. The Wavecom receiver has a poor ability to differentiate between channels, so odds are even if theres a Wavecom signal on another channel, at least a portion of the video will bleed over. Wired video devices would require some extensive video equipment to detect with real certainty, however searching for a syncing frequency will get good results much of the time. Then theres the matter of encrypted video.


    Video streams may be encrypted in any number of ways, though all techniqes may be broken down into analog and digital methods. Analog video encryption typically uses techniques similar to telephone scramblers, while digital encryption methods are equated with computer encryption systems.


    In an analog video encryption system frames from the video stream can be inverted making the picture just about unwatchable, although this certainly doesn't offer the greatest security for a video transmitter. Super-imposing a sine wave whose negative peak met with the video's positive peak over the video signal would cause the receiver to lose synch, making the picture unwatchable. Using a gated synch device that output pulses larger than those of the video signal would also cause a loss of synch.


    Digital video encryption applies an encryption algorithm to a digitized video signal. Popular encryption systems for video include DES and VideoCypher II, though video encryption systems abound.


    Locating cameras through a physical search can be frustrating, as cameras can be easily disguised in common items.



    Any PCs with connected webcams should be checked for trojans such as NetBus and SubSeven , or hostile scripting that could activate the camera.



    Ping sweeps and packet analysis will allow for detection of camera servers connected to a LAN. Servers configured to use a dialup line can be detected through call accounting, or the use of a listen-down amplifier.



  • Countermeasures:


  • Certain video cameras can be nullified by flooding them with either white light (tube based cameras and CCD cameras with intensifiers) or IR light from a set of IR LEDs. As long as the light hits the camera squarely, the camera will be blinded. Then theres spray-paint....


    Suspect PC cameras should be disconnected when not in use. LAN-connected computers with webcams should be firewalled.



  • Further Resources


  • NIJ Guide 201-99, Video Surveillance Equipment Selection and Application Guide <http://www.ncjrs.org/txtfiles1/nij/179545-1.txt>

    Axis, FlexWatch and Leunig all manufacture camera servers.