netmeg - 6:40 pm on Apr 24, 2013 (gmt 0)
The big question for me is - ask your new client if he/she did *anything at all* to obtain these links - did they buy a service, or hire someone to build them, or in any way influence their placement. Then ask them again and decide whether or not they're telling the truth.
From that you should get your answer on what to do next.
I've never done any real linkbuilding in my life (too much work) and I don't worry about garbage scraper links that show up in GWT. I have a ton of them, but I'm not really worried about them.
However I've had clients who have hired services that put them in spammy link directories and link wheels, and I would disavow those in a heartbeat (we didn't have the Disavow tool back when I was I was dealing with that, but I'd probably use it if this situation popped up again with a new client)