[ale] protection from TCP DOS attacks

[Joe Bayes]

I have five machines connected directly to an ISP (no firewall)
through a DSL line. I suspect that I'm being attacked, probably by
ping flood or something, from a specific site from time to time, but I
haven't been able to get any concrete evidence. I am running RH6, with
tcp wrappers installed and tcp syncookies enabled.

1) Is there any attack other than a ping flood which would cause this,
   but would leave no trace in /var/log/messages?
2) Is it possible to turn off a specific site's ability to ping my
   machine, short of my calling up my ISP and having them reconfigure
   their router? I can't seem to find a daemon or an entry in
   inetd.conf...what is it that takes care of responding to pings?
   Rootshell.com simply suggests reconfiguring your router to drop all
   packets from that address, but I would rather take care of it on my
   own if possible. 
3) Failing the above, is there some way to log these attacks, so I can
   be sure that they're actually happenning and aren't just somebody
   ftping a large file somewhere?

Information or pointers to information would be welcome. Thanks.

--joe