I have an ubuntu 11.10 VM running on an OSX machine.
Every once in a while some services become inaccessible from specific IPs (e.g. sometimes just ssh is blocked, and sometimes both ssh and https.)
The blocking of e.g. the ssh isn't per user, since the same blocked user can change his IP and immediately connect successfully that way.
I'm not aware of any special security software that was installed on either the ubuntu nor OSX. Specifically, there's no fail2ban on either of them.
How would I go about investigating which process exactly is responsible for this? Also, how can I try to eliminate the possibility that it's the router which is causing this?