Kick-aha: There's also the PC DRM Database. I can't say how trustworthy it is, but it also includes games not from Steam and has tools to check game directories for possibly applied DRM measures.
the.kuribo: Nice resource, the organization and interface could use some work, but it does seem to have quite a bit of data -- close to 1000 entries if you look at the spreadsheet version. Thank you for sharing!
pedrovay2003: 1. The easiest way is to use a tool called ProtectionID, or PiD for short. It scans entire folders for all kinds of DRM, and if a game has CEG in any of its files, it clearly spells it out as "Valve CEG" in one of the program's windows. The problem with it is that I do believe it was made by pirates, which rubs a lot of people the wrong way, and it does give virus scanners like AVG a false-positive. I've been using it forever, though, and I've never had any problems with anything; I just leave it zipped so AVG doesn't detect it, and when I want to use it, I temporarily disable AVG. The program is completely safe, and I always have a copy of it with me.
2. I just noticed this recently, so I'll have to do some more tests, but if you start a Steam game online for the first time after you download it and you specifically get a Steam popup that says something like completing or finishing installation, the CEG is verifying and customizing your files. This popup is NOT the same as the one that says Steam is installing DirectX and that kind of stuff, it specifically says that it's actually finishing the installation, and it's referring to the game itself. With non-CEG games, I have never once seen that window pop up.
the.kuribo: I appreciate the writeup, it would be great if we could get a master list of CEG affected games going. With respect to PiD, I'm always a bit wary of running unexamined code from untrusted sources. I'd also recommend that you be a bit careful with PiD as even though it may not show any adverse issues on your system yet, good malware is written in a way that it is virtually undetectable. What I usually do with untrusted or potentially suspect code is to only execute it on a spare, isolated testing system that is never connected to LAN or WAN. Additionally, it is best to use unwriteable media (like mastered CD-R that can no longer be written to) to transfer files to the isolated system, so that no data can ever escape it.
Yeah, that's good advice. There's always a risk in situations like that, but I've been using it for so long without any apparent issues that I guess I haven't thought to do any of this; I've even run malware protection programs, and nothing came up.
As far as a list of CEG games goes, this is what I've found so far, both through other websites and my own testing:
007 Legends
3000AD
Aliens: Colonial Marines
Aliens vs. Predator
Bionic Commando
Bioshock Infinite + DLC
Borderlands: The Pre-Sequel
Borderlands 2
Cabela's Dangerous Hunts 2013
Cabela's Hunting Expeditions
Call Of Duty : Modern Warfare 2
Call Of Duty : Modern Warfare 2 - Multiplayer
Call Of Duty : Modern Warfare 3
Call Of Duty : Modern Warfare 3 - Multiplayer
Call Of Duty: Black Ops
Call Of Duty: Black Ops - Multiplayer
Call Of Duty: Black Ops 2
Company of Heroes 2
Company of Heroes 2: Ardennes Assault (with CPUID check)
DeathSpank
DeathSpank: Thongs of Virtue
DiRT Showdown
DoTA 2
Duke Nukem Forever
Evolve Beta (64bit version)
F1 2012
F1 2013/14 (with CPUID check)
F1 RACE STARS
F.E.A.R. 3
Family Guy: Back to the Multiverse
Football Manager 2012
Football Manager 2013
Football Manager 2014/2015
Grid Autosport (with CPUID check)
Grid 2
Hitman: Absolution
Hitman: Sniper Challenge
HOMEFRONT
Just Cause 2
Kane and Lynch 2: Dog Days
Lara Croft and the Guardian of Light
Lara Croft and the Guardian of Light Demo
Left 4 Dead 2
Madballs in...Babo: Invasion
Mafia 2
Prototype 2
Red Faction Armageddon
Risen 2
Saints Row: The Third
Serious Sam HD: The First Encounter
Serious Sam HD: The Second Encounter
Serious Sam 3
Sid Meier's Civilization: Beyond Earth (with CPUID check)
Sid Meier's Civilization V Demo
Sid Meier's Civilization V
Sid Meier's Civilization V - Gods and Kings
Sleeping Dogs
Sniper Elite V2
Sniper Elite Nazi Zombie Army
Sniper Elite Nazi Zombie Army 2
Sniper Elite 3 (with CPUID check)
Space Marine
Spec Ops: The Line
Risen 2
The Amazing Spider-Man
The Bureau: XCOM Declassified
The Darkness II
The Lord of the Rings - War in the North
The Typing of the Dead: Overkill
Total War Rome II
Total War SHOGUN 2
Total War: SHOGUN 2 - Fall of the Samurai
Total War: SHOGUN 2 - Rise of the Samurai
Transformers: Fall of Cybertron
Viking: Battle of Asgard
Warhammer 40,000: Dawn of War II - Retribution Beta
Warhammer 40,000: Dawn of War II - Retribution
Warhammer 40,000: Space Marine - Demo
XCOM: Enemy Within (with CPUID check)
XCOM: Enemy Unknown
The interesting thing here is that Linux seems to have absolutely no CEG support, as games on this list that are on both Windows and Linux will copy/paste like regular games if you do it in Linux.