Dynamic DNS just means you MIGHT get your IP changed.  This isn't done to
prevent "hacking", a terrorist term used to make firewall and antivirus
companies rich.  It's done to prevent users from becoming SERVERS and
using upload bandwidth.  They only time it is changed is when "they"
decide you are a bad boy and need to be put on a rotation to prevent you
from running your server.  Other times, they leave your phone number of
the modem tied to it to keep the load on the DNS servers down, which
makes them run faster for all.

I've had the same IP for years on dynamic DNS cable.  It didn't even
change when I swapped DOCSIS modems.

Everyone you connect to must have your IP to send data back to you.  It
has nothing to do with "hackers" who have no more chance of "getting at
you" one way or the other.  The bad boys operate by installing servers on
your laptop usually sent in a malicious email you opened with a Swiss
Cheeze email client like Outlook or Outlook Express.  If you have no
malware installed, it doesn't matter if anyone calls all 65,535 ports of
your machine.  Your system simply reports the port listening, if some
stupid Windows program, or Windows itself, has forgotten to close
it....or it reports the port closed, go away.....or, if you have a
firewall like you should have, it doesn't answer any calls from any IP it
hasn't called, making you appear invisible.

Now, EVERY OS, all of them, have had some problems with being attacked by
thousands of calls per second or have handled malformed packets sent to
them in an unexpected manner due to screwups by the OS coders.  So, M$
and the other OS coders are always sending out disguised "upgrades" or
"improvements" to cover these tracks as fast as they can.  Here's some
organizations who do NOT sell scare tactics, but are involved in making
the net safe:

http://www.cert.org/
http://www.sans.org/top20/
Microsoft is the biggest target because it has always been the biggest
a.shole in the computer biz.  Any Microsoft product, not just Windows, is
always targeted and has the most known vulnerabilities because of the way
the corporation acts to its users.  Open source software, like Linux, is
just as vulnerable as Microsoft, but, because of its open source hacker
roots is simply attacked much less to find them.  Mac OSX isn't
invulnerable, either.  None of them are.

The number one protection product is Symantec that will ALWAYS have its
"haters" because they charge money for their services.  However, to have
a staff of hackers to find and fix what the bad boys are doing, you need
to PAY them.  I'm paying on all my computers except my Linux tablet.  If
it got trashed, I'd simply reflash its Linux OS and load it back up,
which is just so easy.  The hackers are so busy writing great software
for it, they have no time to attack it...(c;
http://www.symantec.com/index.jsp
I've recently purchased the Norton 360 3-computer deal, dropping my other
Norton subscriptions for NAV and Internet Security I've used for years.  
One license fee for 3 computers, instead of 3 separate licenses.
http://www.symantec.com/norton360/?inid=us_ghp_promo_hero2_norton360

Here's what I'm paying for:
http://www.symantec.com/norton/security_response/threatexplorer/index.jsp
Here's a new worm discovered Apr 30th I won't get:
http://www.symantec.com/norton/security_response/writeup.jsp?docid=2008-
043015-2430-99&tabid=1

The new 360 does a lot more for the browser than the previous products.  
Browsers are much more of a target, now, than your email.  Just browsing
websites is all it needs.  360 goes crazy when it bumps into one it
doesn't like...(c;