You're Being DDOSed — What Do You Do? Name and Shame?

badger.foo writes "When you're hit with a DDOS, what do you do? In his most recent column, Peter Hansteen narrates a recent incident that involved a DNS based DDOS against his infrastructure and that of some old friends of his. He ends up asking: should we actively publish or 'name and shame' DDOS participants (or at least their IP addresses)? How about scans that may or may not be preparations for DDOSes to come?"

Comments

not sure "shame" will have much effect

[Trepidity]

The vast majority of DDoS participants are infected computers in botnets, and their owners are typically unaware. Will they even notice your naming sufficiently to be ashamed? Maybe if it's a corporation it'd have some effect: publishing that you were hit by a DDoS that included X computers from BigCorp might make BigCorp look bad. But not so much if the botnet is a bunch of random home PCs.

No

[Anonymous Coward]

The only reason you can possibly have for publishing the IP addresses is to provoke vigilante justice type of actions, likely counter ddos or something.
What you should do is report him to the abuse department of his ISP. Note the responses of the ISP's and name and shame the ISP's that do not take action.
IP addresses from bad ISP's should end up on a "botnet-friendly ip list" so we can start blocking the traffic from these isp's.

Re:No

[VortexCortex]

Note the responses of the ISP's and name and shame the ISP's that do not take action. IP addresses from bad ISP's should end up on a "botnet-friendly ip list" so we can start blocking the traffic from these isp's.

On a DoS or DDoS (special case of DoS) that's fine. On a reflective DDoS (RDDoS, a special case of both DDoS and DoS) you have a different situation. A denial of service (DoS) is any interruption of service, e.g., by flooding the server with SYN packets. A distributed denial of service (DDoS) is when the attack comes from multiple different places at once, e.g., a single connection may not be enough to take down a server with high bandwidth; However if you coordinate the attack across many different connections then the overall traffic can eclipse even a high bandwidth server. With a DDoS the machines coordinating the attack may or may not belong to the attackers, but it's a good idea to contact the ISPs so that the IP holders can be notified that their systems may be infected with a bot-net -- Although, this may not be the case, as I'll explain later. In a reflective distributed denial of service (RDDoS), the apparent IP addresses may belong to machines that were under the control of any malicious software. Reporting these IPs would be pointless.

When a server receives the first SYN (synchronize) packet of a TCP connection handshake, it replies with a SYN-ACK (acknowledgement & synchronization) to the source IP of the originating packet. Then a ACK is sent to the server to acknowledge the server's synchronization. This verifies both endpoints aren't spoofed. A RDDoS takes advantage of the fact that:
0. The source IP address of the initial SYN packet can be spoofed (the "From" field can be bogus).
1. The server sends a SYN-ACK before the connection endpoints have been verified.
2. The TCP protocol allows several (five) retries of the SYN-ACK packet.

In a RDDoS, a single malicious computer can spoof the "From" IP of a TCP connection, and spray it around to servers on the net. The bogus return IP address is that of the victim system. Thus, legitimate servers will flood the victim's connection with five SYN-ACK packets for each single packet the attacker sends. Thus the victim never has the attacker's IP address. To combat this servers may pro-actively detect an IP that sends too many incomplete TCP connection requests, and block it. However, the attacker can have many IP addresses at their control (see: botnet) limited to just a few packets per hour sent to an entire Internet of servers. None of these infected machines will be revealing their IP addresses when they perform the reflective attack by spoofing the source IPs of their packets. What we need is for ISPs to block packets originating from their network that that don't have correct return IP addresses... Not all ISPs do this.

Now what if the attacker only has a single machine at their control and they perform an RDDoS? Why, the traffic pattern is identical to a DDoS -- Ah, I can hear your gears turning already: Can't the return IP addresses can be checked to see if they're residential IPs, and thus victims of a botnet infection? Yes, but how do you differentiate the non-residential IPs between infected servers and non infected servers? Just assume that the non-residential IPs aren't intentionally malicious? Yes, indeed, which is why RDDoS is a popular form of network DoS.

I reiterate: What we need is for ISPs to block packets originating from their network that that don't have correct return IP addresses; Thus, spoofed packets are dropped at the source. You'd think with deep packet inspection now available this shallow packet inspection would be broadly adopted -- Ah, but this is electrons spent that don't directly benefit profits. IPsec was once a requirement of IPv6 adoption, and would defeat endpoint spoofing, however IPSec has been made optional for IPv6, so we can expect the RDDoS attacks to continue for quite some time.

Two problems with that

[stevegee58]

1) It's DISTRIBUTED. You'd have to name and shame thousands.
2) Many of the DDOS nodes don't know they're being hijacked for a DDOS. Name and shame an innocent person?

A more detailed proposal ...

[Frater 219]

Sites under DoS attack should publish (through a channel not congested by the attack) a list of the IP addresses attacking them, through some trustworthy third party. Then, other sites should subscribe to that list and refuse service to those addresses until they clean up and stop attacking.

For instance, consider your uncle who uses AOL. His computer is infected with botnet garbage and is participating in a DoS attack against (say) Slashdot. Slashdot sends a list of attacking IPs, including your uncle's, to Team Cymru (the third party). Cymru aggregates these and publishes a list, updated every three hours. AOL subscribes to that list. When your uncle goes to check his AOL email, he gets an error: "We regret to inform you, your computer has been hacked, and is being used by criminals to break the Internet. You can't get to your AOL email until you kick the criminals off by installing an antivirus program and running a full scan. Click here to install Kaspersky Antivirus for free. Thank you for helping keep criminals from breaking everyone's Internet. Sincerely, Tim Armstrong, CEO, AOL."

Then your uncle gets mad and calls up AOL and complains. They try walking him through using the antivirus program, but he just curses them out and says he'll go to Hotmail instead. He tries ... but Hotmail also subscribes to the same list and tells him the same thing: "Your computer is infected with malware and is being used to attack other sites on the Internet. You cannot obtain a Hotmail account until your computer is clean. Click here to install Microsoft Antivirus." He gives up and calls AOL back, and they help him get his computer cleaned up. Within half an hour, it's off the botnet; and within three hours, it's off the list of attacking hosts, and your uncle can get his AOL email again.