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98% of DNS Queries at the Root Level are Unnecessary
LEPP writes "Scientists at the San Diego Supercomputer Centerfound that 98% of the DNS queries at the root level are unnecessary. This doesn't even take into account the 99.9% of web pages suck or are unnecessary anyways. This means that the remaining 2% of necessary DNS queries are probably not necessary either."
99% of slashdot posts are unnecessary.
On a similar note, I noticed that AOL causes a lot of DNS lookups. From what I can see from my firewall logs, each TCP connection from an AOL user is handled by a separate proxy. Each proxy then does its own lookup on the host. So, for a normal sized webpage with some images or whatever, you get like 10 TCP connections for the content and 10 UDP connections for the DNS lookup. Seems kind of excessive to me.
is it that hard to configure a firewall to explicitly allow outgoing traffic rather than allow all? It seems that everyone thinks that the only bad traffic is the stuff coming in from the outside...
It's no wonder these servers have so many problems - there's thirteen of them! They need a lucky #14 - a Bilbo Baggins for their horde of dwarves. That'll stop those DoS attacks and unnecessary requests right away!
This doesn't even take into account the 99.9% of web pages suck or are unnecessary anyways.
What standard is this based on? My website wite sucks and is only necessary for my own amusement but it is similar to my favorite kind of sites on the web. I would use the web a lot less if it wasn't for those 99.9% of web sites. Most blogs, for instance, suck and are unnecessary but at the same time the total of all the blogs is having a big impact on news outlets and the media.
FoundNews.com - get paid to blog.,
From the article:
"Researchers believe that many bad requests occur because organizations have misconfigured packet filters and firewalls, security mechanisms intended to restrict certain types of network traffic. When packet filters and firewalls allow outgoing DNS queries, but block the resulting incoming responses..."
It's nice to see a story with info I can take and use. This is actually "stuff that matters".
Kudos to the researchers, and now I am off to check my firewall.
There are 01 kinds of cars in the world. The General Lee, and everything else.
Is it just me, or is this a description of a reverse lookup? How does that qualify as unnecessary? This is a pretty common step in troubleshooting, and some software does a reverse lookup following a forward lookup to verify that the hostname it gets back is the same one it started with.
Chuckles
I see this kind of thing all the time on /.--completely unedited, barely literate, rant-style submissions. Why don't the /. editors tone down or eliminate the rhetoric from submissions about otherwise worthy topics, or at least fix the grammar and typos?
I know, I'm going to get blasted for saying this, but I'm convinced it's one of those "little things" that makes /. look to the rest of the world more like a bunch of know-nothing kids typing at each other than a group of technically literate activists with something of value to contribute.
I now return you to your regularly scheduled rant...
Why don't DNS servers have a list of correct top-level domains, in order to answer directly, without going to a root server? The list is short, compared to the information the DNS server caches already, and the content of the list doesn't change so often. This list could be downloaded once in a day or so, from the DNS root servers.
When packet filters and firewalls allow outgoing DNS queries, but block the resulting incoming responses, software on the inside of the firewall can make the same DNS queries over and over, waiting for responses that can't get through
Why the hell does a firewall accept outgoing queries to black-listed domain names, if they are configured to block the response to these queries? This seems like a serious misconception to me.
JB.
"Scientists at the Vatican Praying Center found that 98% of the prayer queries at the God level are unnecessary."
If the authors actually thought how the DNS works they would realise the reason for this. A DNS server that gets a request for .com will consult the root the first time and then cache the result. So even though the server might then get a million hits in .com it won't ask the root again.
If the server tries to query for a non existent domain it will get back a 'non-existent' response. Now it will cache that response for some time but the chances of getting a cache hit is actually pretty low.
So if you have a properly configured DNS with a bunch of web surfers that view 1 million pages in 20 TLDs and 1,000 bogus ones they will generate 20 hits they would classify as genuine and 1,000 that were 'unnecessary'.
That is how the system is meant to work.
The 70% of repeated requests are likely to include outright attacks as well as misconfigured DNS systems.
The problem dealing with these issues is that a DNS query is pretty cheap to handle, cheaper in fact than most of the proposed defenses. It is probably more expensive for a DNS server to check IPs against a blacklist than to just return the damn data...
Looking for an Information Security student project suggestion?
Try http://dotcrimeManifesto.com/
And that's a problem? My understanding was dealing with this sort of thing was exactly the purpose of the root DNS servers. If every ISP's DNS server was pre-configured to recognize valid and invalid top-level domains, you could just set them up to go straight to the specific DNS servers handling those domains (.com, .net, .org, etc.) There would be no need for a root-level system.
The argument for allowing this kind of cracked query through to the root server is that it makes it easy to add new domains (.elvis, .corp, what have you) without forcing everyone to reconfigure their DNS boxes for each new top-level domain.
How about coming up with a DNS Moderation system.
The root servers give say 50 karma points to each IP address issuing a query.
If the query is unnecessary, it gets modded "-1 redundant".
When karma hits 0, it stops responding to further queries.
DNS eventually stops working at that site, admin pulls head out of ass and fixes the problem causing the redundant DNS queries.
Beauty is in the eye of the beerholder.
It obviously seems to be a lot of junk traffic, but the only part we can say is bad requests are part 3 and 4 from the chart. Bad spellings must go to the root since there may be such domains!
It would be nice to analyze the 70% repeated or identical queries, probably lots of traffic can be explained for (or else there are a bunch of administrators out there who need a good manual on bind).
To do a reverse lookup, the resolver sends a different request type, asking for a PTR resource record. The form is to put the IP address (or network address) backwards, and append
If you have your own DNS server and watch your DNS traffic, you can see these two effects happening differently.
For a forward (A or MX record) lookup:
Local server queries root server for an A record
Root server responds with NS record for the registry of the domain
Local server contacts registry server for A
Registry server responds with NS records for the domain
Local server contacts the domain's server, which responds with an A record
Local server answers the resolver with the A record.
For a reverse (PTR) lookup, the resolver traverses the netblock providers:
Local server queries the root servers with a properly constructed PTR request (z.y.x.w.in-addr.arpa.)
Root server knows only where major net blocks are allocated, and returns the NS record of a Regional Internet Registry (RIPE, APNIC, etc)
Local server again queries an RIR NS with the PTR
RIR NS knows which ISPs hold which blocks, so responds with the ISP NS record
Local server again queries the ISP NS server, which either has the reverse hostname, or once again returns the NS record of the the local DNS server.
The two different types of queries follow different paths, either Name Registries or Netblock Providers. This article points out that many resolvers are broken because they allow obvious reverse lookups to pass as forward lookups, and then can't deal with the resulting error messages.
I have often seen broken resolvers repeatedly query DNS servers I manage, possibly because as the article points out, fucked firewalls allow the requests out, but block the requests from getting back to the resolver. It happens so much I just ignore it when I see it, its not worth notifying the admins because they are usually too clueless to know how to fix the problem.
the AC
Hemos is like...sci-fi fans;he thinks technology is cool, but he hasn't bothered to understand the science it's based on
Well, that's the theory. In practice, however, there are millions of servers out there that do not cache NXDOMAIN at all, and just keep querying, over and over and over again, for TLDs that they've already been told don't exist. Microsoft's name server has been known to do this.
At one point, f.gtld-servers.net was seeing millions of repeated queries per hour from the same two .mil servers asking the same question and refusing to accept the NXDOMAIN. For long periods, these two servers were asking the same question multiple times per click of F's timer. That's.. ummm.. Bad.
I suggest that you read the actual CAIDA paper, and the other papers on the subject that Evi Nemeth and others at CAIDA have produced. They *have* thought about how the DNS actually works in practice. You've only thought about how it would work if every implementation worked perfectly, according to your expectations.