Yup, aware of MS's problem this summer - but I thought you could install robust enough defenses against it. Otherwise why haven't they been brought down again?
Just for the hell of it, I've copied Cisco's recommended prevention measures here just so you can see that I have no possible way of understanding what is and isn't possible with DDoS - LOL!!!
The following are suggested methods to prevent distributed denial of service attacks.
Use the ip verify unicast reverse-path interface command on the input interface on the router at the upstream end of the connection.
This feature examines each packet received as input on that interface. If the source IP address does not have a route in the CEF tables that points back to the same interface on which the packet arrived, the router drops the packet.
The effect of Unicast RPF is that it stops SMURF attacks
(and other attacks that depend on source IP address spoofing) at the ISP's POP (lease and dial-up).
This protects your network and customers, as well as the rest of the Internet. To use unicast RPF, enable "CEF switching" or "CEF distributed switching" in the router. There is no need to configure the input interface for CEF switching. As long as CEF is running on the router, individual interfaces can be configured with other switching modes. RPF is an input side function that enabled on an interface or sub-interface and operates on packets received by the router.
It is very important for CEF to be turned on in the router. RPF will not work without CEF. Unicast RPF is not supported in any 11.2 or 11.3 images. Unicast RPF is included in 12.0 on platforms that support CEF, including the AS5800. Hence, unicast RFP can be configured on the PSTN/ISDN dial-up interfaces on the AS5800.
Filter all RFC1918 address space using access control lists.
Refer to the following example:
interface xy
ip access-group 101 in
access-list 101 deny ip 10.0.0.0 0.255.255.255 any
access-list 101 deny ip 192.168.0.0 0.0.255.255 any
access-list 101 deny ip 172.16.0.0 0.15.255.255 any
access-list 101 permit ip any any
Apply ingress and egress filtering (see RFC 2267) using ACL.
Refer to the following example:
{ ISP Core } -- ISP Edge Router -- Customer Edge Router -- { Customer network }
The ISP edge router should only accept traffic with source addresses belonging to the customer network. The customer network should only accept traffic with source addresses other than the customer network block. The following is a sample ACL for an ISP edge router:
access-list 190 permit ip {customer network} {customer network mask} any
access-list 190 deny ip any any [log]
interface {ingress interface} {interface #}
ip access-group 190 in
The following is a sample ACL for a customer edge router:
access-list 187 deny ip {customer network} {customer network mask} any
access-list 187 permit ip any any
access-list 188 permit ip {customer network} {customer network mask} any
access-list 188 deny ip any any
interface {egress interface} {interface #}
ip access-group 187 in
ip access-group 188 out
If you are able to turn on Cisco Express Forwarding (CEF), the length on the ACLs can be substantially reduced and thus increase performance by enabling unicast reverse path forwarding. In order to support unicast reverse path forwarding, you only need to be able to enable CEF on the router as a whole; the interface on which the feature is enabled does not need to be a CEF switched interface.
Use CAR to rate limit ICMP packets.
Refer to the following example:
interface xy
rate-limit output access-group 2020 3000000 512000 786000 conform-action
transmit exceed-action drop
access-list 2020 permit icmp any any echo-reply
For more information, refer to IOS Essential Features.
Configure rate limiting for SYN packets.
Refer to the following example:
interface {int}
rate-limit output access-group 153 45000000
100000 100000 conform-action
transmit exceed-action drop
rate-limit output access-group 152 1000000 100000
100000 conform-action
transmit exceed-action drop
access-list 152 permit tcp any host eq www
access-list 153 permit tcp any host eq www
established
In the above example, replace:
45000000 with the maximum link bandwidth
1000000 with a value that is between 50% and 30% of the SYN flood rate
burst normal and burst max rates with accurate values
Note that if you set the burst rate greater than 30%, many legitimate SYNs may be dropped. To get an idea of where to set the burst rate, use the show interfaces rate-limit command to display the conformed and exceeded rates for the interface. Your objective is to rate-limit the SYNs as little as necessary to get things working again.