Access to the Internic Blocked

Curtis wrote:

I've said many times that if security in your network is weak enough
that you need to worry about LSRR packets you need to worry about
security in your network.

Not at all. LSRR is a nice tool to mount practically untraceable
flooding attack (hint -- just forge source address and spread
intermediate points evenly across the network). Shutting you
down may be exactly what the attacker wants.

(LSRR attacks against service providers are particlularly bad --
just imagine somebody flooding you at T-1 speed and bouncing
packets back and forth two dozen times. Poof -- here goes the
T-3 :slight_smile:

There are particularly nasty man-in-the-middle attacks (which
defeat one-time-password login authentication, like that) if you
can combine LSRR with bogus routing.

The minute someone unpacks a Sun workstation, configures an IP address
and sticks it on the ethernet without installing the security patches
and doing the administrative work needed to secure the machine, if you
had a small hole in your security with LSRR, you now have a gaping
hole in your security. If you are relying on blocking LSRR, your
security is a weak as the most peerly administered machine on your
network. A real bad thing if you are constantly hiring.

I never argued that blocking LSRR plugs all security holes. However
it is one thing _not_ used in normal operations; and everything not
used _must_ be shut down by a prudent security. And, again, there
are several LSRR-based attacks.

Even so, if anywhere, where you want LSRR turned off is the border
router(s) in front of the machines used for operations, network
management, etc.

Obviously you want your network to be secure even if
LSRR was enabled for the reason I cited above.

Security Rule #1: You're never secure. Turning LSRR off doesn't
particularly hurt connectivity, and is cheap. It's a way to _improve_