The Constant Blinking of the cable modem is part of how the Internet cable system works if you have a Router you should Not be concerned about it.
Win XP has remote assistance system if you do not need it switch it Off.
If there are other computers on your private network you have to check their setting and make sure that none of them generates such request.
If your Router has a uPnP capacity and you do not need it Switch it Off.
As for the Internet.
Since you have a Router, unless you set it specifically open ports that are associated with Remoter request toward your computer's IP, traffic from the outside should Not reach your computer.
There is No point to try to track this incidences because there are constant probing like this on the Internet most done by automatic bots and they do not attack you specifically since you are on Dynamic ISP connection and No one really knows that "you is you".
Protect your system and enjoy your Internet connection.
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