One of our competitors recently shut down. Instead of just taking their site down, they decided to redirect all their traffic to us with a 302 redirect. All of the traffic is redirected to us with the original path from their site, resulting in 404 pages. Most of the arriving traffic is directly from Google search results that still point to the old site.
Goolge now thinks we have 10s of thousands of 404 pages, as indicated by Google webmaster tools. It also provides a very bad user experience for those people arriving on our site's 404 page when they expected to get to another site, which makes us look like we hijacked the original site.
The incoming requests don't have any particular identifying detail what we can use to pinpoint they came from that redirect, as far as I can tell. The HTTP referer is from the originating source (typically Google).
Is there a way stop this from happening? should we try and find their hosting provider and get them to take it down? is there anything on our side we could do prevent this?