[TelstraClear] TCL cannot block a DNS DOS attack on my account, costing 50gb usage a day

Forums › Vodafone New Zealand › [TelstraClear] TCL cannot block a DNS DOS attack on my account, costing 50gb usage a day

scottq

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Topic # 114771 2-Mar-2013 20:26

Partly my fault, I had a recursive DNS server on my network which should have been accepting only authoritative requests - Stupid I know but I had a hardware failure and had to configure this machine up quickly and missed this out.

Anyway, noticed my inbound traffic spike to around 5mbps (constant) and narrowed it down to one host hitting port 53 hard. I've updated my FW to drop the packets and have null routed them just for extra sanity, then called TelstraClear.

The tech I spoke to repeatedly said it was my responsibility to filter the traffic even after explaining I had already done so and the only further steps I could take to stop the traffic hitting my modem was to turn it off.

I've spoken to several different techs/customer support people and they have explained they don't have the tools to filter this particular traffic to my IP address. Their reason was it could be legitimate traffic.

My question to you all, is surely this can't be true. They manage the network and should mitigate what could be classed as a DOS attack on one of their customers.

My account is at 100% utilisation and around 50Gb per day and they can't block it.????!?!

Zeon

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Reply # 773712 2-Mar-2013 20:34

The thing is their routers probably don't have the processing power for per packet port inspection. Usually providers will null route an IP address if required but not filter on port.

My suggestion would be to change IP addresses.

scottq

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Reply # 773717 2-Mar-2013 20:45

I've provided them with the IP address, they could null route it.

Zeon

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Reply # 773720 2-Mar-2013 20:50

scottq: I've provided them with the IP address, they could null route it.

So the requests are only coming from a certain IP address which you want to block? Or do you mean you have multiple IP addresses and you have asked telstra to null route the one being hit?

If its coming from just a single source I don't think they can null route that as if they did it router wide, it would affect potentially tens of thousands of users who may want to legitimately connect to that IP. If it were only for you it again by a source/destination IP match and processing requirements go up considerably. Some providers offer this on a managed firewall service.

sbiddle

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Reply # 773724 2-Mar-2013 21:01

One person supports this post

Best approach is to get them to change your IP address.

Ragnor

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Reply # 773749 2-Mar-2013 22:56

Unfortunately this is the typical level of support you can expect from Telstraclear.

Work a saw a similar problem (dhcp denial of service type attack) last year on a business fibre connection with them and they wouldn't do anything to help with cut the problem off upstream.

In the end I think they convinced them to write off the usage after much haggling and threatening to switch to a different provider.

There are plenty of good other good providers for business connections these days, if you have control over the decision don't let poor service like this stand... Unleash, Vibe, Voyager, DTS, Vocus/Maxnet etc.

TelstraClear

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TelstraClear

Reply # 774175 4-Mar-2013 10:54

Hi Scott. Can you please PM me your account number so we can investigate, and a contact name and number as well please? As others have pointed out, it's likely that the solution is to change your IP address.

Cheers, Gary

NonprayingMantis

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Reply # 774177 4-Mar-2013 10:59

If the rating of traffic happens before traffic hits your modem (which seems likely), even turning off your modem probably won't make any difference to your usage spike

TelstraClear

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TelstraClear

Reply # 774200 4-Mar-2013 11:30

Hi Scott - we think we've found your account and will have a look, however the highest data usage was about 12.7GB a day on 11-Feb and was 2.5GB yesterday. These are total (up plus down). Do you have another account where the usage was 50GB? If so, please can you let me know that account number so we can investigate.

Cheers, Gary