Outgoing connection to multiple IP/port combinations

Hi,

i'm running a CraftBukkit Server for some days now and everything works well so far. I installed some plugins which all work well but a day or two ago i started seeing this in my log:

The reason these connections fail is due to my firewall. I only allow known in- or outgoing connections. I wonder where these come from suddenly. I can't remember having a plugin that needs external connection to work (apart from the mcdigr plugin, but i've setup this port to go through the firewall which works well).

It looks like this comes from the same plugin or other source as it always happens in blocks or at the same time of a minute (see seconds of the log file above).

these are the plugins instsalled so far:

Any idea?

Thanks for helping!