Access on Port 0

["Christian Schuerer-Waldheim" <csw@xray.at>]

Hello!

In my firewall-log I can find several entries like this:

----8<-----------
Oct 11 19:25:48 asterix kernel: Dropwall: IN=eth0 OUT=
MAC=ff:ff:ff:ff:ff:ff:**:**:**:**:**:**:**:** SRC=***.***.***.***
DST=***.***.***.*** LEN=1456 TOS=0x00 PREC=0x00 TTL=110 ID=21266 PROTO=UDP
SPT=17060 DPT=0 LEN=1436
----8<-----------
[Real IP's and MAC removed]

I did some research and find out, that there is no port 0 (and I was shure
that I have no service running on port 0 (it's even not possible)).

So, what could this be? What could it be good for trying to connect to a not
existing port? Is it a kind of scan? Somewhere on the internet I've read
that in this way you can find out which OS is runnig.

Thanks for your help!

Christian