I never take the Current Anonymous Users counter too seriously--HTTP users are difficult to measure because there is not a 1:1 relationship between users and connections. It is possible that a search engine is parsing your site. In that case, all requests would probably be directed to a single server. It?s also possible that it?s simply a false alarm. I have seen this happen on stand-alone IIS servers (both IIS4 and IIS5). If it is not affecting performance, I would not spend any time worrying about it.
At a minimum, I would make sure that requests sent to that server aren?t being queued up and therefore causing performance to suffer. Use the Performance administrative tool to measure HTTP response time, or simply point your browser at the affected server when the number of anonymous users spikes.
This was first published in May 2001