Discover the steps you can take to regain control of your DNS traffic and prevent cybercriminals from using DNS to attack your organization This infographic provides eight DNS-based attacks your organization should know about…. Malicious newly registered domains are used in cybercrime, such as in phishing and malware distribution, and often result in credential and data theft….
Fast flux is a technique cybercriminals use to cycle through bots and DNS records, usually for phishing. It is difficult for law enforcement to detect…. By submitting this form, you agree to our Terms of Use and acknowledge our Privacy Statement. Log4j Resource Center. Research Partner Customer Employee.
DNS Security. Take a test drive. Get the white paper Watch the video. Learn more. What it means for you. In geek terms, that's called Resolution. The mechanics of DNS can be quite complicated, as information isn't held in a single database, but rather distributed in a worldwide directory including a vast number of DNS servers. Fortunately, the average internet user doesn't normally have to get involved in any of the low-level technical details. Cloudflare has focused much more on the fundamentals.
Privacy is another major highlight. Cloudflare doesn't just promise that it won't use your browsing data to serve ads; it commits that it will never write the querying IP address yours to disk.
Any logs that do exist will be deleted within 24 hours. And these claims aren't just reassuring words on a website. Cloudflare has retained KPMG to audit its practices annually and produce a public report to confirm the company is delivering on its promises. The 1. These are very generic - you get one set of instructions for all versions of Windows, for instance - but there are some pluses IPv6 as well as IPv4 details and you should be able to figure it out.
The product doesn't offer ad-blocking or attempt to monitor what you can access, and what you can't. The one caveat is that Cloudflare has introduced content filtering for malware and adult content blocking, with their 1. If you have any problems, Cloudflare offers a community forum where you can ask questions or see what others are doing, a nice extra touch which we'd like to see followed by other providers.
Privacy can't quite match the 'we don't keep anything' promises of Cloudflare, but it's not bad. The service logs the full IP address information of the querying device for around 24 to 48 hours for troubleshooting and diagnostic purposes. There's a further benefit for experienced users in Google's detailed description of the service. If you'd like to be able to assess the significance of Google's privacy policy , for instance, you can read up on absolutely everything the service logs contain to find out for yourself.
Google's support site offers only very basic guidance targeted at experienced users, warning that "only users who are proficient with configuring operating system settings [should] make these changes. The company sells itself on its ability to block malicious domains by collecting intelligence from 'a variety of public and private sources.
That's a little too vague for us, and we're not convinced that using a large number of threat intelligence providers will necessarily help — the quality of the intelligence is generally more important than the quantity. There's no arguing about Quad9's performance, though. DNSPerf currently rates it seven out of ten for average worldwide query times, lagging behind Cloudflare and OpenDNS, but effortlessly outpacing contenders like Comodo. Drilling down into the detail reveals some variations in speed - Quad9 is in eighth place for North American queries - but overall the service still delivers better performance than most.
Setup guidance is a little limited, with tutorials for the latest versions of Windows and macOS only. They're well presented, though, and it's not difficult to figure out what you need to do.
Commercial plans enable viewing a history of your internet activity for up to the last year, and can optionally lock down your system by allowing access to specific websites only. These aren't going to be must-have features for the average user, but if you're interested, they can be yours for a modest fee.
Comodo Group is the power behind a host of excellent security products, so it's no surprise that the company also offers its own public DNS service. It doesn't just block phishing sites, but also warns if you try to visit sites with malware, spyware, even parked domains which might overload you with advertising pop-ups, pop-unders and more.
Comodo claims its service is smarter than average, too, detecting attempts to visit parked or 'not in use' domains and automatically forwarding you to where you really want to go. Performance is key, of course, and the company suggests its worldwide network of servers and smart routing technology give it an advantage.
Unfortunately, Comodo stats weren't that impressive, and in our tests, we got an average query time of around 72ms. Cache poisoning attacks There are several variants of DNS spoofing attacks that can result in cache poisoning, but the general scenario is as follows: The attacker sends a target DNS resolver multiple queries for a domain name for which they know the server is not authoritative, and that is unlikely to be in the server's cache.
The resolver sends out requests to other name servers whose IP addresses the attacker can also predict. In the meantime, the attacker floods the victim server with forged responses that appear to originate from the delegated name server.
The responses contain records that ultimately resolve the requested domain to IP addresses controlled by the attacker. They might contain answer records for the resolved name or, worse, they may further delegate authority to a name server owned by the attacker, so that they take control of an entire zone. If one of the forged responses matches the resolver's request for example, by query name, type, ID and resolver source port and is received before a response from the genuine name server, the resolver accepts the forged response and caches it, and discards the genuine response.
Future queries for the compromised domain or zone are answered with the forged DNS resolutions from the cache. If the attacker has specified a very long time-to-live on the forged response, the forged records stay in the cache for as long as possible without being refreshed.
In an amplification scenario, the attack proceeds as follows: The attacker sends a victim DNS server queries using a forged source IP address. The queries may be sent from a single system or a network of systems all using the same forged IP address. The queries are for records that the attacker knows will result in much larger responses, up to several dozen times 1 the size of the original queries hence the name "amplification" attack. The victim server sends the large responses to the source IP address passed in the forged requests, overwhelming the system and causing a DoS situation.
In Google Public DNS, we have implemented, and we recommend, the following approaches: Securing your code against buffer overflows, particularly the code responsible for parsing and serializing DNS messages.
Overprovisioning machine resources to protect against direct DoS attacks on the resolvers themselves. Since IP addresses are trivial for attackers to forge, it's impossible to block queries based on IP address or subnet; the only effective way to handle such attacks is to simply absorb the load. Implementing basic validity-checking of response packets and of name server credibility, to protect against simple cache poisoning. These are standard mechanisms and sanity checks that any standards-compliant caching resolver should perform.
There are many recommended techniques for adding entropy, including randomizing source ports; randomizing the choice of name servers destination IP addresses ; randomizing case in name requests; and appending nonce prefixes to name requests. Below, we give an overview of the benefits, limitations, and challenges of each of these techniques, and discuss how we implemented them in Google Public DNS.
Removing duplicate queries , to combat the probability of "birthday attacks". Rate-limiting requests , to prevent DoS and amplification attacks. Monitoring the service for the client IPs using the most bandwidth and experiencing the highest response-to-request size ratio. Implementing basic validity checking Some DNS cache corruption can be due to unintentional, and not necessarily malicious, mismatches between requests and responses e. We recommend and implement all of the following defenses: Do not set the recursive bit in outgoing requests, and always follow delegation chains explicitly.
Disabling the recursive bit ensures that your resolver operates in "iterative" mode so that you query each name server in the delegation chain explicitly, rather than allowing another name server to perform these queries on your behalf. Reject suspicious response messages. See below for details of what we consider to be "suspicious". Do not return A records to clients based on glue records cached from previous requests.
For example, if you receive a client query for ns1. Rejecting responses that do not meet required criteria Google Public DNS rejects all of the following: Unparseable or malformed responses. Responses where key fields do not match corresponding fields in the request.
Records which are not relevant to the request. Records in the answer, authority, or additional sections for which the responding name server is not credible. We determine the "credibility" of a name server by its place in the delegation chain for a given domain. Google Public DNS caches delegation chain information, and we verify each incoming response against the cached information to determine the responding name server's credibility for responding to a particular request.
Adding entropy to requests Once a resolver does enforce basic sanity checks, an attacker has to flood the victim resolver with responses in an effort to match the query ID, UDP port of the request , IP address of the response , and query name of the original request before the legitimate name server does. Randomizing source ports As a basic step, never allow outgoing request packets to use the default UDP port 53, or to use a predictable algorithm for assigning multiple ports e.
Randomizing choice of name servers Some resolvers, when sending out requests to root, TLD, or other name servers, select the name server's IP address based on the shortest distance latency.
Randomizing case in query names The DNS standards require that name servers treat names with case-insensitivity. One significant challenge we discovered when implementing this technique is that some name servers do not follow the expected response behavior: Some name servers respond with complete case-insensitivity: they correctly return the same results regardless of case in the request, but the response does not match the exact case of the name in the request.
Other name servers respond with complete case-sensitivity in violation of the DNS standards : they handle equivalent names differently depending on case in the request, either failing to reply at all or returning incorrect NXDOMAIN responses that match the exact case of the name in the request.
Prepending nonce labels to query names If a resolver cannot directly resolve a name from the cache, or cannot directly query an authoritative name server, then it must follow referrals from a root or TLD name server. For example, the. In other words, requests to ccTLD name servers for resolution of such hostnames will not result in referrals, but in authoritative answers; appending nonce labels to such hostnames will cause the names to be unresolvable. That is, there are some name server hostnames that happen to live in a gTLD zone rather than in the zone for their domain.
A gTLD will return a non-authoritative answer for these hostnames, using whatever glue record it happens to have in its database, rather than returning a referral. For example, the name server ns3.
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