Is MY System is Hacked

Hi
every One I am new user of this software

I see the log
in which i see the following message
Description Inbound Policy Violation (access denied, IP= xxx.xxx.0.45, port=nbdgram(138))
Protocol UDP Incoming
Source: xxx.xxx.0.45:nbdgram(138)
destination xxx.xxx.0.255:nbdgram(138)
Reason: Network Control Rule ID = 5

Well i am using internet through cable my ip is also some what in same local domain
say xxx.xxx.0.87

Now I want to know weather these guys are trying to hack my systems
or it is normal because i saw in logs of other ips like.xxx.0.56 or xxx.xxx.0.94 etc

second what is Network Control Rule ID=5
what is this NBDGRAM

I know the question are so many but i hope you will answer all my question…
which is detected my another application

Details Attempted Intrusion “Portscan” against your machine was detected and blocked
Intruder : xxx.xxx.o.1 (domain(53))
Risk Level: Medium
protocol: UDP
Attacked Ip: xxx.xxx.0.87
attacked port 1906

in next attack
port is 1148

well i want to know from this weather my service provider is trying to hack my PC or some one else in the same domain…

Thanks in advance
dhir…
(:NRD)