numerous "portscan" attacks on my computer

Two months after i installed norton 360 v2.0 and i checked the log for the first time. And i saw quiet a few intrusion: portscans
Details:
Attempted Intrusion "Portscan" against your machine was detected and blocked.
Intruder: 202.79.32.98(domain(53)).
Risk Level: Medium.
Protocol: UDP.
Attacked IP: my ip.
Attacked Port: 61889.


The problem is that the ip 202.79.32.98 is supposed to be my dns ip(or something). And sometime its 202.79.32.97. But both are my ISP's dns ip(according to my friends with same ISP)

another 1 for reference

Attempted Intrusion "Portscan" against your machine was detected and blocked.
Intruder: 202.79.32.97(domain(53)).
Risk Level: Medium.
Protocol: UDP.
Attacked IP: my ip.
Attacked Port: 59828

Aside from that i have a dynamic ip. Attack comes sometimes as soon as i connect to the net even if its 4 in the morning. Could this be coming from someone specific?

What should i do? Thanks in advance