Security Issue?

[Sacto]

I turned on console debug and on reviewing the log contents and I've noticed a lot of those 'Bad challenge from..." messages. I understand the about the variable that can be turned on for this but I think this is something different.  Any ideas (is it a hacker?)  There are hundres of lines of this; here's a sample:

04/25/2007 - 17:01:36
Bad challenge from 68.51.93.140:2643.
Bad challenge from 68.51.93.140:2645.
Bad challenge from 68.51.93.140:2647.

04/28/2007 - 18:20:31
Bad challenge from 189.157.46.122:3001.
Bad challenge from 189.157.46.122:3003.
Bad challenge from 189.157.46.122:3005.
Bad challenge from 189.157.46.122:3007.
Bad challenge from 189.157.46.122:3009.
Bad challenge from 189.157.46.122:3011.
Bad challenge from 189.157.46.122:3013.
Bad challenge from 189.157.46.122:3015.
Bad challenge from 189.157.46.122:3017.
Bad challenge from 189.157.46.122:3019.
Bad challenge from 189.157.46.122:3021.
Bad challenge from 189.157.46.122:3023.
Bad challenge from 189.157.46.122:3025.
Bad challenge from 189.157.46.122:3027.
Bad challenge from 189.157.46.122:3029.
Bad challenge from 189.157.46.122:3031.
Bad challenge from 189.157.46.122:3033.
Bad challenge from 189.157.46.122:3035.
Bad challenge from 189.157.46.122:3037.
Bad challenge from 189.157.46.122:3039.
Bad challenge from 189.157.46.122:3041.
Bad challenge from 189.157.46.122:3043.
Bad challenge from 189.157.46.122:3045.
Bad challenge from 189.157.46.122:3048.

[Drocona]

Shouldn't be any problem at all, they show up every now and then, mostly they are server list search engines (like gametiger.net), I always ignore them, I've NEVER been hacked in any way.