After weeks of occasional mystery outages on our office network, lasting minutes to hours, always ending as mysteriously as they started, this morning I was able to get into the router and get something that looks an awful lot like a smoking gun: connection attempts to port 80 on a single IP address from 725,000+ machines around the world.
The catch? The destination address wasn’t on our network. It belongs to an ISP in Spain.
So, somehow, our ISP’s global routing table decided to forward this attack to us. Given that their response to the previous outages was “gee, looks fine to us”, I’m looking forward to eavesdropping on our network manager’s conversation with them.