The potential damage of large-scale cyber or space conflict remains difficult to determine, largely because digitization and the use of orbital satellites on a large scale represent relatively new commercial realities and the world has never had to deal with one (or all) of the advanced economies suddenly losing Internet access or GPS coverage. Nonetheless the reliance on orbital imaging and digitized networks for both commercial supply chains and military command and control imply a tremendous and difficult to unwind reliance on space and cyber assets in the 21st century. As a result a straight-forward analysis of the basic asymmetries of modern space and cyber deterrence seems in order.
Space deterrence relies on the currently prohibitive costs of space-launch technology. Deterring a non-space power remains a trivial concern because without orbital launch technologies attacking a space-based power's orbital systems is essentially impossible (barring some massive advances in lasers or other direct-energy weapons). Similarly mature space powers have each other in a natural deterrence posture; all space powers can directly threaten the satellites of all other space-faring countries and rely intensely on their own satellite systems in times of war as well as peace, while the anti-satellite (ASAT) weapons of any one state will inevitably generate debris that harm all others. As a result hesitance to engage in first use (advantages are fleeting) and a willingness to join in cartel-like behavior to minimize ASAT use (in order to minimize externalities).
Unfortunately a major transition zone exists between non-space powers and their mature counterparts. These transitional countries, arguably including the People's Republic of China and potentially soon including North Korea and Iran, do not intensely rely on orbital systems yet possess the ability to place payloads in orbit with reasonable reliability. This allows for a first-use mentality (there's little to lose and potentially much to gain) while auguring for a "spoiler" mentality in space-weapons limitation efforts (why protect the prerogatives of relative hegemons?). This critical juncture occupied by rising space powers, particularly if they feel threatened by established space-faring states, threatens the stability of orbital access due to the destabilizing structural tendency to ASAT first strikes in the event of conflict.
Space weapons are ferociously difficult to assess due to the fact that no two nations with major orbital operations have ever entered a formal shooting war with one another. Cyber weapons escalate these complications to an enormous degree because of vastly lower barriers to entry, increased difficulty of attribution, and a vastly wider and more complicated array of potential targets. As a result a fuller examination of cyber deterrence (and the difficulties therein) awaits future posts.