I see, interesting. I can understand that a solominer of this scale would need fewer resources than a proxy. It would be fun to know exactly how much resource would be needed.
Tough to say exactly what you'd need to respond to it, but just some rough numbers. Assuming a 1 million bot botnet (which might be conservative):
If each bot checks in once per minute to see if the block has changed, you're looking at 16.6k connections per second. Lets assume its still using HTTP just for simplicity. The response will be ~200 bytes including headers/overhead give or take if no block change has occurred, and ~300 bytes if it did (a response would have to include wallet address, prevblockhash, and difficulty). A block change every 10 minutes would mean every 10 minutes you have 2375 bytes of data being transferred, per bot.
That comes out to 1.95 gigabytes per 10 minutes, or 27 mbps. You'd probably have a fairly even distribution since each bot started at different times, though it would actually be 25 mbps 9 minutes out of 10, and 38 mbps for the minute after a block change.
16.6k connections per second is the real bottleneck there. However, if the system was distributed to where the slaves contact any one of 25 cheap $5 VPSes, you have about 600 connections per second, and each VPS would only need ~1 mbps of transfer. Basically 1 hour worth of bot activity would likely pay for an entire month of servers. They could add/remove servers quickly and use DNS as a method for distributing the bots without a central control location.
The above is why I stated this type of activity is scary, even though it is inevitable. You're looking at a system that could easily grow to make up a majority of the network, for a few hundred dollars a month in expenses to the operator. It can, and eventually will make mining unprofitable for any legitimate party*. It would be good for network security, unless it was turned into a 51% attack attempt. Alternatively, it could be a sort of strangulation attack, where the the botnet is pumping out 0 tx blocks, and difficulty gets driven up to the point legit blocks can't fit all the transactions into them, causing a growing backlog.
*: By "any legitimate party" I'm not including very small miners. While some people do have free electricity, very few can grow beyond a few GPUs before a landlord gets suspicious/angry. And even then, it could reach the point where the mining income doesn't match the cost to replace dying hardware.
