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Cyber Underground: Overcoming Obstacles to Cyber in Subterranean Warfare

Wild Blue Yonder / Maxwell AFB, AL --



The possibility of the subterranean operational area emerging as a new war-fighting domain has some validity. While there are both proponents and detractors concerning domain establishment, one thing is certain: subterranean warfare exists and is growing more prevalent. With terrorist and drug smuggling organizations globally using tunnels, mines, and other subterranean infrastructure such as subway tunnels and sewers, the need to effectively engage these power structures where they operate is growing rapidly. However, the nature of the subterranean space is such that communication, wireless transmission, and other cyber-dependent systems are in many cases effectively squelched, leaving military forces figuratively and literally in the dark.

To gain insight into how to ameliorate the issues posed in the cyber domain for subterranean warfare (STW), it is important to understand how this environment is defined and what types of advantages, limitations, and challenges characterize this environment. Advantages in STW can equate to the obvious available obfuscation both physically and virtually and can also include the ability to reach areas unreachable within other operating environments. The limitations of STW are of deep concern for military forces facing an unconventional foe. The lack of communications, low-to-no light conditions, and often unbreathable air are major hindrances. Other challenges may include the operational advantage subterranean adversaries possess due to living and working for long stretches within this space. This can offer a distinct “home-field advantage” to well-practiced and trained unconventional forces.

Current technologies fail to provide rapid mapping and persistent situational awareness of the diverse subterranean operating environment; however, there is technological hope on the horizon, aimed at removing such obstacles.
Removing the subterranean warfare obstacles currently encumbering US force
Current technologies fail to provide rapid mapping and persistent situational awareness of the diverse subterranean operating environment; however, there is technological hope on the horizon, aimed at removing such obstacles.
Photo By: DARPA
VIRIN: 200507-F-YT915-005

(DARPA image)

Figure 1. Removing the subterranean warfare obstacle currently encumbering US force. Current technologies fail to provide rapid mapping and persistent situational awareness of the diverse subterranean operating environment; however, there is technological hope on the horizon, aimed at removing such obstacles.

Fortunately, the US individual and joint military forces are trained and equipped for STW. There are various tactics, techniques, and procedures (TTP) used throughout the military branches to combat forces who operate increasingly beneath the traditional battlefield domains. However, while conventional forces, special forces, and logistics support for STW are fairly robust, there are gaps within the cyber operations (CO) and information warfare (IW) spectrum of war fighting. Signals traditionally employed within the electromagnetic spectrum cannot penetrate many of the dense materials that comprise the subterranean operating environment. Transmissions that are general line of sight get lost or are garbled. Radios, wireless devices, and other communications media becomes virtually useless.

There is technological hope on the horizon to remove the STW obstacles currently encumbering CO and IW. Ground-penetrating signals, new communications devices, and improved TTPs related to cyber within this difficult operating environment are being researched and tested. Exercises and scenarios are increasingly inclusive of STW, further bolstering military force capability and adaptability. Additionally, growing cyber capabilities within other domains are likely to add resources previously unrealized, making STW a more navigable battlespace.

The Subterranean Operating Environment

STW offers several advantages, limitations, and challenges to US forces. As with any unfamiliar or underutilized operating environment, defining the characteristics of STW are often based on lessons learned from past experience either operationally or within exercises. An Army first lieutenant gives some insight into a decision he made during an exercise regarding a tunnel: “‘Sir, what do you want us to do about the tunnel?,’ one of my squad leaders asked [during] a training exercise in. . . . Nowhere in my training had tunnels come up or been addressed as a tactical problem. ‘Seal it, post security, and we’ll deal with it later.’”1 This is unfortunately apparently an all-too-common reaction to STW challenges. Some of the reluctance to engage likely comes from a lack of understanding of the subterranean operating environment, but a very important issue accompanying the extant anxiety connected with STW is the lack of equipment and resources for fighting in this dark underworld. This is a brief picture of the limitations and challenges encountered in STW and will be more fully explored. There are also advantages to be had in STW, but unfortunately those capitalizing on these limitations and challenges currently are US adversaries. However, US military forces are beginning to make advances in this possibly emergent domain and have good reason to do so.

A great deal of attention has been given to STW of late, with adversaries like Daesh using underground tunnels they constructed and existing infrastructure to sneak past US and allied forces. This subterfuge, along with numerous other examples, has prompted US military senior leaders to give greater scrutiny to the US military’s current capabilities in STW. In 2018, Lt Gen Robert Ashley, director of the Defense Intelligence Agency, said at the Defense One Technology Summit in Washington, DC: “Subterranean is something we are going to have to contend with in the future. You look at the electrical systems . . . control systems, control grids.”2 Lieutenant General Ashley even went on to volunteer that a subterranean domain could be added to US military doctrine in the near future. Regardless, the subterranean operating environment is a growing area of interest across all services in the US and globally. “By 2030 two-thirds of the world’s population will be living in cities, the urban population in developing countries will double, and the area covered by cities could triple, according to a United Nations report [in 2016].”3 This population projection is important for two important reasons: first, subterranean and urban war-fighting environments share many common TTPs, and second, many of the people living in these large cities and megacities of the future will live underground. As military engagements sometimes move into urban areas, this becomes a huge area of concern. This further highlights the areas of advantage found by adversaries in the subterranean realm. “‘They’ve gone underground to match our overmatch,’ said retired Army Maj John Spencer, chair of Urban Warfare Studies with the Modern War Institute at West Point.”4 This is in relation to the superior war-fighting capabilities US forces bring to bear in almost every domain. Terrorist organizations across the globe are using this tactic to frustrate US conventional war fighters and reaping the benefits in the process. But this is not only an issue with nongovernmental organizations like Daesh but with peer adversaries as well. “It is happening in Syria now. Iraqi forces faced it in Mosul. Russia, China, North Korea, and Iran all boast complex facilities laced with reinforced command and control and the ability to deploy thousands of troops, tanks, missiles, even launch planes from underground runways.”5 These advanced STW capabilities are only the bud of a massive rhizome within the subterranean operating environment. This reality has led recently to US military leaders expressing the desire to have advantage or at least parity with currently skilled subterranean adversaries. “Leading voices in the Army have argued for the creation of a “megacities combat unit,” trained at a special school.”6 Along with this recommendation, new technologies (to be discussed), training, and education are being plied for use in STW, leading to potential advantages in the near future.

Limitations are a constant in any domain or war-fighting environment. Space is limited through tyranny of distance, lack of gravity, and high-cost runs. Ground is limited by inability to see over the horizon, sea by speed and direction, air by fuel capacity and weight requirements, and cyber by connectivity and access. STW, most assuredly, has limitations for anyone who seeks to operate in this difficult and dangerous space. “It is darkness like you’ve never seen. The air you breathe could kill you in moments. All of your fire support—air, armor, artillery—is useless. The walls and ceiling could collapse. Communications will fail. A wrong turn leaves you utterly alone.”7 These limitations are compounded by the fact that underground and urban spaces are often very cramped, restricting freedom of movement. Altogether, STW is characterized as much by its limiting attributes as its material composition. “Subterranean space can be generally defined as space that complies with one of the mentioned conditions: - it has no visual contact with the surface; - it has no direct functional connection with the surface, - its dimensions enable basic life-supporting functions, - life-supporting conditions are ensured by/even primitive) technology.”8 This definition of subterranean space gives a perspective on not only the potential limitations to be found in this realm, but the very archaic and peculiar state of the environment. Of course, the subterranean environment drives limitations and threats in cyber to a great extent. “Despite medical advances and overall population stabilization, the past 100 years of human activity has created a new domain that is susceptible to devastating cyberattacks: the subterranean.”9 Of course, this relates to industrial control systems and supervisory control and data acquisition (SCADA), the systems that control everything from subway trains to sewer flow control valves. These subterranean systems have been, and in many places, remain vulnerable to all manner of attacks. One such event that has generated a mixture of disbelief and ire involved a disgruntled former employee at Australia’s Maroochy Shire Sewage facility. “In November 2001, 49-year-old Vitek Boden was sentenced to two years in prison for using stolen wireless radio, SCADA controller and control software to release up to one million liters of sewage into the river and coastal waters of Maroochydore in Queensland, Australia.”10 The release of sewage into the natural environment was a natural disaster, the scope of which is still being felt in the Queensland area. The event caused untold devastation to property, wildlife, and the river system, killing at the very least, tens of thousands of aquatic creatures.

Challenges within the subterranean operating environment abound. Not only do the limitations discussed previously present obstacles to communication and cyber exploitation, the marked advantage adversaries possess present several, difficult barriers within STW. Walker Mills gives some insight into this advantage as he quotes and comments concerning the misgivings of an Air Force officer: “’Subterranean warfare may be the answer for the enemies of the United States.’ For much of the era of manned flight, combatants have consistently gone underground in the face of enemy air superiority—either in strike capability or reconnaissance.”11 This is a very real problem considering the massive labyrinth of caves, tunnels, and subterranean infrastructure comprising the STW battlespace. As adversaries move underground, the capabilities tied to the new IW paradigm such as cyber and intelligence, surveillance, and reconnaissance face new challenges as well. “One of the Air Force’s key advantages is its cutting-edge intelligence, surveillance and reconnaissance (ISR) capabilities. But those eyes in the sky—everything from remotely piloted aircraft to specialized recon aircraft like the Rivet Joint to satellites—can be stymied by tunnels or other underground facilities concealed beneath massive amounts of dirt and rock.”12 If the US military’s most powerful assets are effectively blinded and rendered useless by dirt and rock, there is a massive challenge to be overcome. This is compounded by other technological and communications complexities that will have to be overcome to effectively prosecute STW. “The subterranean is a “complex” operating environment that presents unique monitoring and communications challenges.”13 While the challenges are myriad, there is hope of overcoming or at least mitigating these obstacles with new technologies and capabilities while simultaneously endeavoring to train and educate US forces for the future of STW.

New and Future STW Tech and Capabilities

While the challenges and limitations for cyber and IW in STW are plentiful, they are not going unmatched. New technologies and capabilities are being researched and developed to combat and mitigate the various and numerous obstacles accompanying STW. An unconventional, but powerful example of cyber power within the last few years is the Stuxnet cyberattack on the Iranian nuclear facility in Natanz. “A cyber-based attack, as shown in the Stuxnet incident, is a valid option against underground facilities. This form of attack limits exposure and risk to ground forces. Cyber-based attacks have mitigated other underground threats in the past. Given the lack of training in and doctrine for subterranean operations, electronic warfare (EW) should be further explored and incorporated to fill this gap.”14 Interestingly, the information related capabilities (IRC) of EW and cyber are two components of IW. Bowes et al., go on to include another IRC in the IW panoply. “If shown to be viable, MISO [Military information support operations] can influence the audience through themes, messages, and actions such as contaminated air supply, structure collapse, food/supply shortage, fire/smoke inhalation, flooding, tunnel remediation, social media, and local populace engagement. MISO can assist US forces in shaping the information environment to persuade, change, or influence the behaviors of those associated with a subterranean threat.”15 Coupled with new enabling technologies for ISR, the full arsenal of IW can be brought to bear, projecting further power into the STW environment. Other nations are increasing their capabilities to combat and operate in STW. One of the Israeli Defense Force (IDF) primary adversaries, Hamas, has shown extensive prowess in STW, penetrating IDF walls, facilities, and other physical defenses. As a result, IDF has turned its formidable resources and military capability toward Hamas’ network of tunnels. “The idea that the group has been able to cause what little damage it has may be even more meaningful given the extensive resources that go into Israel’s maintaining a very capable and sophisticated military operation, including substantial resources devoted to locating and eliminating Hamas tunnels.”16 Rounding out the full spectrum of IW IRCs, ISR collection and analysis has great applicability in unearthing STW attributes and location data. “In many areas, imagery intelligence (IMINT) exists or may be requested to support analysis. Also, measurement and signature intelligence (MASINT) platforms can be leveraged to provide closer analysis of known underground structures. Multi-spectrum imagery may be able to detect surface anomalies that could indicate subsurface vents, intakes, or portals.”17 Altogether, existing and growing capabilities within the individual IRCs and the combine IW paradigm indicate an advanced and progressive reach into the STW sphere.

Additionally, various new technological advances are lending support to new and existing IRCs, advancing IW capability now and into the future. One of the biggest obstacles for cyber and communications technology in the subterranean operating environment is the solid soil, wall, and other composite structures that are impenetrable by most radio waves. As a result, accomplishing IW within the STW realm is very difficult to nearly impossible. However, new transmission technologies are changing this once impossibly intransigent environment, using new signal theory and waveform transmissions to circumvent these barriers. “Wireless Underground Communication Networks (WUCNs) constitute one of the promising application areas of the recently developed wireless networking techniques. The WUCNs consist of wireless devices that operate below the ground surface. These devices are either (i) buried completely under dense soil or (ii) placed within a bounded open underground space such as underground mines and road/subway tunnels.”18 WUCN technology certainly shows promise through the use of signal propagation previously unknown. The technology rests on the use of electromagnetic (EM) and magnetic induction (MI) capabilities using soil as the transmission medium. This technology is extremely important not just for communications and cyber applications for military STW use, but for emergency communication for miners, subway operators, and various other subterranean applications. Ryerson University researcher Xavier Fernando is interested in these applications by implementing a technology called radio signals over optical fibers (ROF): “ROF is already used to provide wireless-communication access to the $985-million Niagara Tunnel, a massive hydroelectricity project sponsored by Ontario Power Generation.”19 This technology is well-suited for mining operations where infrastructure can be laid. However, more flexibility is necessary for STW. Fortunately, more technologies are being advanced for STW more specifically. In a report from the Center for Disease Control, one of these technologies is discussed. “[A contractor] delivered its explosion-proof UHF-MF (Ultra-High Frequency to Medium Frequency) Bridge. This deliverable uses standard, approved UHF radios on a medium frequency system. The bridge was tested successfully at the National Institute for Occupational Safety and Health Safety Research Coal Mine using UHF handheld radios approved by the Mine Safety and Health Administration.”20 This type of radio system offers more flexibility and promise for STW. The ability to transmit through the use of RF wave technology is much closer to the capability US subterranean forces need. Another report from the Office of Energy Efficiency and Renewable Energy provides more information on a subterranean wireless technology called Digital Through-The-Earth (TTE) Communication System. “TTE can provide vital underground communications for the mining industry, urban first-responders, and others who frequently work underground. The system can increase underground mining production and safety through improved communications that can monitor orientation and position of individual miners and mining equipment.”21 These technologies are being leveraged and researched in concert with other tech to establish a true STW capability that is on the horizon. “A major project that, if successful, could transform situational awareness for troops underground, is the Defense Advanced Research Projects Agency (DARPA) Subterranean Challenge. Launched in 2017, it aims for new ways of mapping underground tunnels and meeting the array of challenges with technology by 2021.”22 This advancement project includes technologies like robotics and autonomous subterranean drones, breaching technologies, MESH network radios, and various other tools, weapons, and tech for STW. Robotics and drones are also being tested for use in STW. While it used to be necessary to send in human “tunnel rats” with flashlights and a handgun, now radio-controlled equipment can serve the same purpose. “One robot the Army is looking at . . . has demonstrated some of its equipment to both the Army’s Rapid Equipping Force and Marine Corps officials . . . a diesel-powered robot that can operate continuously for 8–10 hours in confined spaces. It is controllable wirelessly to 1 km. . . . Troops are using throwable robots to investigate what’s down the tunnel or passageway. Those can also be fitted with chemical sensors to detect threats. Those include the First Look 110 and the PackBot 510.”23 With all these technologies combined with the cyber and IW capabilities immediately in play, STW is rapidly becoming a more solid operating environment for US STW forces.

Technologies like robotics and autonomous subterranean drones, breaching technologies, MESH network radios, and various other tools, weapons, and tech for subterranean operations are key to military and commercial actors in the domain.
New technologies
Technologies like robotics and autonomous subterranean drones, breaching technologies, MESH network radios, and various other tools, weapons, and tech for subterranean operations are key to military and commercial actors in the domain.
Photo By: DARPA
VIRIN: 200507-F-YT915-006

(DARPA image)

Figure 2. New technologies. Technologies like robotics and autonomous subterranean drones, breaching technologies, MESH network radios, and various other tools, weapons, and tech for subterranean operations are key to military and commercial actors in the domain.


Cyber and IW are areas finding application within every domain to include air, land, sea, and space. However, with other spaces such as the subterranean operating environment, these capabilities are discovering obstacles. To communicate and leverage cyber, IO, EW, and ISR IRC within the greater IW construct, EM and MI signal propagation must be advanced such that they are applicable to STW. While several barriers still exist to cyber and IW, new technologies are paving the way for US forces to dig, tunnel, and win in subterranean space.

Dr. Joshua A. Sipper

Dr. Sipper (PhD, Trident University) is a professor of cyberwarfare studies at the Air Force Cyber College, Air University, Maxwell AFB, Alabama.


1 Walker Mills, “The Elephant in the Tunnel: Preparing to Fight and Win Underground,” Modern War Institute, 19 March 2019, https://mwi.usma.edu/.

2 Patrick Tucker, “ ‘Underground’ May Be the U.S. Military’s Next Warfighting Domain,” Defense One, 26 June 2018, https://www.defenseone.com/.

3 Edith M. Lederer, “UN Report: By 2030 Two-Thirds of World Will Live in Cities,” Associated Press, 18 May 2016, https://apnews.com/.

4 Stephen Losey and Todd South, “The Air Force’s Struggle to Fight Subterranean Warfare,” Air Force Times, 11 March 2019, https://www.airforcetimes.com/.

5 Losey and South, “The Air Force’s Struggle.”

6 Mills, “The Elephant in the Tunnel.”

7 Losey and South, “The Air Force’s Struggle.”

8 Tomaz Novljan, “Underground Spaces/Cybernetic Spaces,” Urbani Izziv 11, no. 2, Drugačno bivanje/Different Living (December 2000): 153–56, https://www.ceeol.com/.

9 Colby Proffitt, “And after the Space Force, a Subterranean Force?,” Fifth Domain, 9 August 2018, https://www.fifthdomain.com/.

10 Gregory Hale, “Classic Hacker Case: Maroochy,” Industrial Safety and Security Source, 22 September 2010, https://isssource.com/.

11 Mills, “The Elephant in the Tunnel.”

12 Losey and South, “The Air Force’s Struggle.”

13 Proffitt, “And after the Space Force.”

14 Joshua S. Bowes et al., “The Enemy Below: Preparing Ground Forces for Subterranean Warfare,” Naval Postgraduate School, December 2013, https://calhoun.nps.edu/.

15 Bowes et al., “The Enemy Below.”

16 Nicole J. Watkins and Alena M. James, “Digging into Israel: The Sophisticated Tunneling Network of Hamas,” Journal of Strategic Security 9, no. 1 (2016): 84–103, https://scholarcommons.usf.edu/.

17 Bowes et al., “The Enemy Below.”

18 Ian F. Akyildiz, Zhi Sun, and Mehmet C. Vuran, “Signal Propagation Techniques for Wireless Underground Communication Networks,” Physical Communication 2, no. 3 (September 2009): 167–83, https://www.sciencedirect.com/.

19 Ryerson University, “Innovative Technology for Wireless Underground Communication,” Ryerson University, 29 November 2010, https://phys.org/news/.

20 Centers for Disease Control, “Mining Contract: Subterranean Wireless Electronic Communication System,” National Institute for Occupational Safety and Health, accessed 26 April 2020, https://www.cdc.gov/.

21 Energy.gov, “Digital Through-The-Earth Communication System,” Office of Energy Efficiency and Renewable Energy,” accessed 26 April 2020, https://www.energy.gov/.

22 Todd South, “The Tech It Takes to Fight Subterranean,” Military Times, 26 February 2019, https://www.militarytimes.com/.

23 South, “The Tech It Takes.”

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