RE: RE: Why blocking bogons buys you nothing (Mikael Ols son)

[TSimons () Delphi-Tech com]

Just some information/stats from another bogon user. We block Bogons, then
rouge/unused ports.

In a period of 3 hours, here are the blocked packet counts from our routers.
Note: we do NOT block access to our corporate web site, nor to our smtp
servers which are the only services that we really have available to the
public.

    deny ip 61.0.0.0 0.255.255.255 any (476 matches)
    deny ip 62.0.0.0 0.255.255.255 any (278 matches)
    deny ip 80.0.0.0 0.255.255.255 any (250 matches)
    deny ip 81.0.0.0 0.255.255.255 any (362 matches)
    deny ip 148.203.0.0 0.0.255.255 any
    deny ip 148.204.0.0 0.3.255.255 any (2 matches)
    deny ip 148.208.0.0 0.15.255.255 any
    deny ip 148.224.0.0 0.15.255.255 any (228 matches)
    deny ip 148.234.0.0 0.0.255.255 any
    deny ip 148.240.0.0 0.7.255.255 any (2 matches)
    deny ip 148.248.0.0 0.1.255.255 any
    deny ip 148.250.0.0 0.0.255.255 any
    deny ip 150.0.0.0 0.0.255.255 any
    deny ip 150.2.0.0 0.1.255.255 any
    deny ip 150.4.0.0 0.3.255.255 any
    deny ip 150.8.0.0 0.7.255.255 any
    deny ip 150.16.0.0 0.15.255.255 any
    deny ip 150.32.0.0 0.31.255.255 any
    deny ip 150.64.0.0 0.31.255.255 any
    deny ip 150.96.0.0 0.3.255.255 any
    deny ip 150.100.0.0 0.0.255.255 any
    deny ip 164.0.0.0 0.31.255.255 any
    deny ip 164.32.0.0 0.7.255.255 any
    deny ip 164.40.0.0 0.0.255.255 any
    deny ip 210.0.0.0 0.255.255.255 any (440 matches)
    deny ip 211.0.0.0 0.255.255.255 any (335 matches)
    deny ip 217.0.0.0 0.255.255.255 any (638 matches)
    deny ip 218.0.0.0 0.255.255.255 any (556 matches)
    deny ip 219.0.0.0 0.255.255.255 any (542 matches)
    deny ip 220.0.0.0 0.255.255.255 any (424 matches)
    deny ip 221.0.0.0 0.255.255.255 any (364 matches)
    deny tcp any any eq 22
    deny tcp any any eq 57
    deny tcp any any eq 81
    deny tcp any any eq sunrpc
    deny tcp any any eq 135 (6572 matches)
    deny udp any any eq netbios-ns (72 matches)
    deny tcp any any eq 445 (200 matches)
    deny tcp any any eq 1002
    deny tcp any any eq 1080 (2 matches)
    deny tcp any any eq 1081
    deny tcp any any eq 1433
    deny tcp any any eq 2112
    deny tcp any any eq 55555


-----Original Message-----
From: Mikael Olsson [mailto:mikael.olsson () clavister com]
Sent: Sunday, November 09, 2003 1:07 PM
To: Stephen Gill
Cc: firewall-wizards () honor icsalabs com
Subject: Re: [fw-wiz] RE: Why blocking bogons buys you nothing (Mikael
Olsson)




Stephen Gill wrote:
> I'd like to point out a few issues with your report as I tend to 
> disagree with it :).

Argumentation good. Shoot.


> ] Why Blocking Bogons Buys You Nothing
>
> This title is misleading.  [...]
> I think you mean to say: "Why Blocking Inbound Bogons Buys You Very Little
> on Firewalls"

Indeed. I added the "Inbound" clause to the title of 
http://www.clueby4.org/pubs/blocking-bogons.txt


> Blocking Bogons buys you a LOT, you just don't
> get to see the benefits because others are doing it for you. 

Actually, don't you mean egress spoofing protection here?
That's a totally separate issue.


> So why are we drawing global conclusions from a _single_ site? 

Because from what I've seen, that's pretty much what everyone else
is doing in when it comes to bogons :)

This MAN has about five or six thousand public IPs, spread out over
five or six disjoint spans. It's got plenty of people that are likely
to attract DDoS attacks (IRC weenies), and indeed, they do happen.

It's not the uunet backbone, but, in my opinion, it's representative
enough for my target audience.


> Many DDOS attacks I see still use random spoofed sources.  Most DDOS 
> attack data points to bogon filtering having a _significant_ impact 
> on reducing the overall load reached on the target network.

40-50% is not "significant" for a DDoS in my opinion. Especially
not if you're doing it on the wrong end of your Internet connection.


> ] Blocking the 0/8 network, 127/8 network and 224/3 networks is another
> ] thing altogheter; there are firm technical and security reasons for
> ] doing that.
>
> There are other networks that will never be part of the global Internet
> routing table, such as but not limited to RFC 1918 space.

Yes, but the technical reasons are not the same.

- 0.* is good to drop because of dumb software that assumes that if 
  the first byte of the IP address is 0, it's uninitialized or 
  otherwise has a special meaning

- 127.* is good because lots of dumb software think that packets 
  sourced from 127.* couldn't have come across the network

- 224.* and up is good because you don't want to end up sending responses
  to multicast addresses that end up getting forwarded to thousands
  of hosts/routers


> [... snip lots of argumentation related to me not putting
>  "inbound" in the title. It's there now.]



-- 
Mikael Olsson, Clavister AB
Storgatan 12, Box 393, SE-891 28 ÖRNSKÖLDSVIK, Sweden
Phone: +46 (0)660 29 92 00   Mobile: +46 (0)70 26 222 05
Fax: +46 (0)660 122 50       WWW: http://www.clavister.com
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