A Sentinel for every man, woman, and child in Zion. That sounds *exactly* like the thinking of a machine to me.

—Morpheus, The Matrix Reloaded

I tried to sell some stuff on Craigslist this week. In both cases, I received exactly one inquiry about the product, from an "out-of-state buyer", offering a check with "$50 extra for your honesty" if I'd ship the product once the check arrived.

I co-authored an unpublished paper on scams like this during graduate school; suffice to say, this should be fun…at least, for me.

Obvious tells:

• They claimed to be out-of-state (legitimate buyers are never out-of-state on Craigslist)
• They offered to send the check even after I said I'd sold the item to a different buyer; a legitimate buyer would never do this.
• They initially messaged me over text (SMS), but switched numbers mid-transaction. Their explanation: "I'm using my friend's phone". What really happened: their SMS provider shut them down due to fraud complaints, and they opened a new account on a different number.

And yet, the biggest tell—but also the most subtle—was that I knew I was talking to a bot—software.

• "David Albrecht this is Luke buying your (Juniper SRX-100 8-port router (DHCP/Firewall) with rackmount bracket - $200)" - a human would never repeat the exact, character-for-character text of my listing, with embedded parentheses and matching capitalization
• Two identical requests, one and then a repeat several hours later, asking me to confirm something. Character-by-character identical—same spacing, misspellings, and capitalization—humans don't behave this way.
• Repeated use of my full name (David Albrecht); humans don't do this.

It was like Morpheus said: the thinking of a machine.

USPS tracking of the "check"