CEG (Custom Executable Generation) is Valve
's alternative to the pitfalls of DRM and part of Steamworks
, the company's free suite of publishing and development tools. What this technology does is register each copy of a game unique to one user, who can then use the title between compatible PCs without any kind of limits or root kits.
Steamworks was also updated with support for in-game DLC
and matchmaking, the latter of which many have enjoyed for quite some time in the PC version of Left 4 Dead