CM1000 protection for DDOS attacks?

> Does the CM1000 include protections for DDOS attacks?  [...]

   It's a modem.  I wouldn't expect it to protect against anything,
except, perhaps, a small child from a light rain.  A router might look
more closely at the data passing through itself.

> [...] I've read that the broadcom chip includes some built in
> protections, [...]

   You read what, exactly, where, exactly?  I'd guess that Broadcom
makes more than one variety of chip.