I very much doubt you are being hit by a DDoS attack. As from what I'm aware you do not run a major website/service & I also doubt you would be able to see one with the equipment/software you have.
You are most probably being hit with viruses that are trying to attack the RPC port. Most of our firewalls are hit around 3-5 times per/sec with these. You may also be hit with the occasional port scanner & web bot/spider.
The best way to secure yourself against these possible attacks is to install a NAT based router if your running either DSL or ISDN (Basically nothing can get back in through the way it operates).
There is also a small chance that you may have a virus that allows access to your computer and opens up an outbound port that then allows access back in again (normally to open the pc up as an open mail server).
If you are convined someone is targetting you need a record of the following for each attack:
1. Time of packets
2. Source IP address
3. Port Number
The port number will allow you determine what type of possible attack it is.
If you then decide to take further action you can find who/where the packets are coming from by looking at the various IP address assignment authorities.
You can then contact the relevant company/ISP/backbone provider with the time & port details and ask for action to be taken.
As an example here is a trace I did on the IP addresses when the forums where hit:
81.80.105.229
Ripe assigned range (81.80.105.224 - 81.80.105.231) 8 adresses 81.80.105.224/29 (255.255.255.248)
[French IP address related to COMMUNAUTE COMMUNES AGGLO DE V via FRANCE TELECOM TRANSPAC]
24.240.103.126 24-240-103-126.charter.com
ARIN assigned range (24.240.0.0 - 24.241.255.255) 131072 addresses (ISP)
[American ISP, Charter - www.charter.com]
80.161.229.106 cpe.atm2-0-1051113.0x50a1e56a.albnxx12.customer.tele.dk
Ripe assigned range (80.161.229.96 - 80.161.229.127) 32 addresses 80.161.229.96/27 (255.255.255.224)
[Danish ISP, TDC - www.tdc.dk, Range assigned as TDC Bredbaand Professional users]
200.227.56.187 200227056187-dial-user-ECP.acessonet.com.br
LACNIC/Registro.br range (200.227.0.0 - 200.227.128.255) 32640 addresses (ISP)
[Brazilian ISP, Click 21 - www.click21.com.br]
DeepBlue
The coder formerly known as Twynklet.