Firewall Wizards mailing list archives
Re: Smurfs and fraggles
From: Bennett Todd <bet () newritz mordor net>
Date: Tue, 16 Feb 1999 14:29:38 +0000
1999-02-11-20:43:53 Bennett Todd:
[ a note talking about configuring packet-filtering firewalls to block these attacks, suitable for deployment on the upstream end of your link ]
and somehow I got myself confused and repeatedly suggested that traceroute uses UDP echo, which of course it doesn't; it uses UDP packets on a series of high-numbered addresses, and generates its reports based on the errors they return, using incrementing TTLs. I knew this, I did, really.... Thanks to Carson for calling my attention to this braino gently. As far as I can tell, the rest of the article stands unchanged, if you just drop all mention of traceroute. So you can block ICMP echo reply altogether and lose use of ping. You can drop UDP echo and lose nothing anyone would miss. You can block them more cleverly and allow legitimate traffic while blocking these DOS attacks. But your blocks only protect the links past the place where you apply them; the blocked attacks will still hammer everything upstream of your firewall. Far, far better if the attack couldn't be effectively mounted in the first place. You should of course have proper filters in place to ensure that your net cannot be used as an amplifier to help attack someone else (accept no incoming packets to the IP broadcast addresses). And you should likewise have filters in place so your net cannot originate packets with forged source addresses. -Bennett
Current thread:
- Re[2]: Smurfs and fraggles, (continued)
- Re[2]: Smurfs and fraggles dcostello (Feb 10)
- Re: Smurfs and fraggles Barrett G. Lyon (Feb 10)
- Re: Smurfs and fraggles Arnd Vehling (Feb 10)
- Re: Smurfs and fraggles Ted Doty (Feb 11)
- Re: Re[2]: Smurfs and fraggles Dani Arbel (Feb 11)
- Re: Smurfs and fraggles Robert Graham (Feb 10)
- RE: Smurfs and fraggles John McDonald (Feb 10)
- Re[2]: Smurfs and fraggles dcostello (Feb 11)
- Re: Smurfs and fraggles Bennett Todd (Feb 11)
- Re: Smurfs and fraggles Laurent LEVIER (Feb 12)
- Re: Smurfs and fraggles Bennett Todd (Feb 17)
- Re: Smurfs and fraggles Bennett Todd (Feb 11)
- Re: Re[2]: Smurfs and fraggles Ryan Russell (Feb 11)
- Re[2]: Smurfs and fraggles dcostello (Feb 10)