The process of using stalker-like tactics to figure out the mental or emotional state of another person in lieu of just asking them.
The person receiving the attention is being stalkered.
Not to be confused with stalking, in which the person is actually obsessed with someone.
Bob: "I wanted to see if Megan was over her ex, so I logged into her Verizon account to check out how often they still text each other."
Bill: "Wow that's some clever stalkering, what did you find?"
Bob: "They were texting at 3 AM the other night. I'm gonna dump that ho!"