I’m not asking if Tor is secure, I’m asking if an observer can know you are using Tor? For example if a persons ISP or company network monitors traffic would they be able to determine with certainty that a person is using Tor or not? For example, the exit nodes certainly are known, though I’m uncertain if the first node the traffic gets passed to is (publicly known)? A sys admin would be able to perform a whois and find out that it’s a tor relay node (if they really wanted to know), wouldn’t they?
As @Manumit asks “If anyone can pitch in on the missing piece, is “obfs3, scramblesuit, fte, and obfs4″ ample obfuscation then?”