
24 Oct 2018
What is DNS Cache Poisoning (and How To Prevent It)
Also known as DNS spoofing, DNS cache poisoning is an attack designed to locate and then exploit vulnerabilities that exist in a DNS, or domain name system, in order to draw organic traffic away from a legitimate server and over to a fake one.
The threat of DNS cache poisoning made the news earlier this year in April when crypto giant MyEtherWallet’s DNS servers were hijacked and redirected legitimate users over to a phishing website.
As a result of the cache poisoning, multiple users were deceived into giving up their wallet keys before transferring their cryptocurrencies into another digital wallet associated with the hackers. All in all, the hackers stole around a hundred and sixty thousand dollars worth of Ethereum before the problem was identified and stopped.
This is just one example that illustrates how dangerous DNS cache poisoning can be. Another reason this kind of attack is dangerous is because it can easily spread from one DNS server to the next.
In this article, we’ll cover the subject of how DNS cache poisoning works and then some solutions you can apply to stop it should it ever happen to you.
How Does DNS Cache Poisoning Work?
Each time your browser contacts a domain name, it has to contact the DNS server first.
Domain Name Servers (DNS) are the Internet's equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses.
This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses.
The server will then respond with at least one IP address (but usually more) for your computer to reach the domain name. Once your computer connects to the IP address, the DNS converts the domain name into an IP address that your computer can read.
Right now, your internet service provider is running multiple DNS servers, each of which caches (or saves) information from other servers as well. The Wi-Fi router you have in your home essentially acts like a DNS server as well, as it caches information from the servers of your ISP.
A DNS cache is “poisoned” when the server receives an incorrect entry. To put this into perspective, it can occur when a hacker gains control over a DNS server and then changes information in it.
For instance, they may modify the information so that the DNS server would tell users to look for a certain website with the wrong address. In other words, the user would be entering the ‘correct’ name of the website, but then be sent to the wrong IP address, and specifically, to a phishing website.
Earlier, we mentioned that one of the reasons why DNS cache poisoning is dangerous is because how quickly it can spread from one DNS server to the next. This is accomplished if and when multiple internet service providers are receiving their DNS information from the now hacker controlled server, which results in the ‘poisoned’ DNS entry spreading to those ISPs to be cached.
From that point on, it can spread to other DNS servers and home routers as well as computers will look up the DNS entry only to receive the wrong response, resulting in more and more people becoming a victim of the poisoning. Only once the poisoned cache has been cleared on every affected DNS server will the issue be solved.
How To Protect Against DNS Cache Poisoning
One of the tricky aspects of DNS cache poisoning is that it will be extremely difficult to determine whether the DNS responses you receive are legitimate or not. In the case of My Ethereum Wallet, they had very limited means to prevent the situation from occurring, and the issue was ultimately solved by their server providers.
Fortunately, there are still a number of measures that your organization can take to prevent such an attack from happening to you, so you should not be under the impression that DNS cache poisoning is impossible or nearly impossible to prevent.
For example, one thing you should do is have your DNS servers configured by an IT professional to rely very little on relationships with other DNS servers. This makes it much harder for a cyber-criminal to use their DNS server to corrupt their targets, meaning your own DNS server is less likely to be corrupted, and therefore you (and everyone in your organization) are less likely to be redirected to an incorrect website.
You can furthermore have your DNS servers configured to only store data that are related specifically to the requested domain and to limit query responses to only provide information that concerns the requested domain as well. The idea is that the server will be set up so that required services are the only ones permitted to run. By having additional services that are not required to run on your DNS server, you greatly increase the odds of an attack happening.
You should also ensure that the most recent version of the DNS is being utilized. This is because the most recent versions will use security features such as port randomization and transaction IDs that are cryptographically secure to help guard against poisoning attacks.
Another important defense against DNS cache poisoning, as MyEtherWallet advised in an announcement following the attack that occurred back in April 2018, is to look for the company’s name in the address bar (so in their case ‘MyEtherWallet Inc’).
This means the site is using an EV SSL/TLS certificate. This would help prevent people from falling victim to a poisoning attack, because they would make sure not to enter their personal details in to a hacker’s website. Not all companies use EV on their websites, so this isn’t a foolproof measure, but it can be a helpful tool when trying to determine if you’re on the right site.
An SSL/TLS certificate is simply a small data file installed on a web server that can bind the details of your organization to a cryptographic key. After it has been installed, the certificate will activate HTTPS protocol to enable a secure and encrypted connection between a browser and your web server. In the case of EV SSL/TLS Certificates, some of those organization details, including the company name as mentioned above, will be presented directly in the browser UI.
Conclusion
In summary, DNS cache poisoning is when an attacker exploits a DNS server to send a forged DNS response that will be cached by legitimate servers.
Subsequently, users who visit the corrupted domain will be sent to a new IP address that the hacker has selected, which is usually a malicious phishing website where victims can be manipulated into downloading malware or submitting login or financial details.
Taking the steps above will help defend your organization against DNS cache poisoning attacks.
About the Author
Sam Bocetta is a freelance journalist specializing in US diplomacy and national security, with emphasis on technology trends in cyber-warfare, cyber-defense, and cryptography.
Note: This blog article was written by a guest contributor for the purpose of offering a wider variety of content for our readers. The opinions expressed in this guest author article are solely those of the contributor and do not necessarily reflect those of GlobalSign.
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GlobalSign Privacy Policy Version 3.1
Updated June 5, 2018
GlobalSign respects your right to privacy. This privacy policy has been developed to inform you about the privacy practices followed by GlobalSign in connection with its websites, products and services. This privacy policy does not apply to GlobalSign services offered by or through our partners, resellers or other third parties, or other third party services or websites, and we encourage you to read the privacy policies of those parties.
This privacy policy will inform you about what data is collected, how we use such data, where data is processed, how you may opt out of your data being used, the security provisions around storing your data and how to correct, update or delete your data.
1. Data Controller
The data controller for personal data collected within the EU is GMO GlobalSign, Ltd., having its registered offices at Springfield House, Sandling Road, Maidstone, Kent, ME14 2LP, United Kingdom. All questions or requests regarding the processing of data may be addressed to: dpo@globalsign.com.
2. Collection of Personal Information
We collect information from you when you (i) place an order for a GlobalSign digital certificate product or other product or service, (ii) scan your servers for digital certificates using our Certificate Inventory Tool (CIT), (iii) apply for access to our managed service platforms, (iv) subscribe to our newsletter, (v) use our online chat service, (vi) download a white paper, (vii) register for a webinar, (viii) respond to a survey, (ix) fill out a form for pre/post sales assistance, (x) open a support ticket, or (xi) your use of social media.
GlobalSign is a Certification Authority and trusted third party. To fulfill requests for digital certificates or other products or services, you may be asked to enter your name, email address, physical address, phone number, credit card information and/or organizational details or other personal information.
- - Contact information such as your name, email address, physical address, and phone number.
- - Relationship information that helps us do business with you, such as the types of products and services that may interest you, contact and product preferences, languages, marketing preferences and demographic data.
- - Transactional information about how you interact with us, including purchases, inquiries, customer account information, billing and credit card information, organizational details, transaction and correspondence history, and information about how you use and interact with our website.
We may develop and acquire additional information about you using third-party (public and private) data sources such as third party databases and government agencies, as well as your browsing and purchasing history in order to process orders for certificates and to improve our services.
GlobalSign treats personal information as confidential, except for the information included in an issued digital certificate. Such information may be verified using third party commercial and government resources, and as such, is deemed to be public information.
3. Purpose of Processing
Your personal data will be used for the purposes specified below:
3.1 To process applications for GlobalSign products and services
Your information is used to provide our products and services and order processing as well as to conduct business transactions such as billing.
3.2 To improve customer service
Your information helps us to more effectively respond to your pre/post sales requests and provide technical support.
3.3 To send renewal notices
The email address you provide for order processing may be used to send you renewal notices for your expiring digital certificate.
3.4 To send service updates
In addition, subject to your consent where required, we may send you new service updates, security updates, related product or service information, and status updates on maintenance windows or service availability.
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Subject to your consent where required, we may send you periodic company newsletters, information about our products and services that may be of interest to you based on your use of other GlobalSign products and services, your attendance at GlobalSign sponsored marketing events such as webinars, your requests for information about similar products and services, or your sharing of data with social media sites such as LinkedIn or Facebook.
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We will process your data for the purpose of performance of our contract with you or the legitimate interest of GlobalSign, which are our usual business activities. In other cases, we will request your consent for the processing of the personal data you may submit.
Your refusal to provide personal data to us for certain products and services may hinder us from fulfilling your order for those products or services. Also, if you deny or withdraw your consent to use personal data or opt out of receiving information about GlobalSign products and services this may result in you not being made aware of renewal notices, periodic company newsletters, new service updates, security updates, related product or service information, and status updates on maintenance windows or service availability. See Section 10 below for how to withdraw your consent.
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The GlobalSign Certificate Center (GCC) uses cookies to enable the fulfillment of services. Cookies may be used when you log into the GCC, purchase products or use certain GCC functions.
In addition, like most online businesses, GlobalSign uses cookies and web beacons on our websites and through marketing related emails to gather and analyze some personal data such as the visitor's IP address, browser type, ISP, referring page, operating system, date/time and basic geographical information.
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We do not sell or trade your personal information to outside parties.
Within GlobalSign: GlobalSign is a global organization with business processes and technical systems in various countries. As such, we may share information about you within our group company and transfer it to countries in the world where we do business in connection with the uses identified in section 3 above and in accordance with this Privacy Policy. In cases where your personal data is transferred to countries that do not provide an adequate level of protection according to the European Commission ('adequacy decision'), we ensure your data is protected by entering into agreements containing standard contractual clauses approved by the European Commission with each of our group companies. A copy of these agreements may be obtained by contacting us as outlined in section 15 below.
Third Parties: We may also transfer your personal data to trusted third parties and our partners in order to serve purposes that are specified in section 3 above. GlobalSign uses a third party to process credit card payments and provides credit card numbers and identifying financial data directly to the third party credit card processor.
In circumstances where data is shared with such third parties, they are required to comply with confidentiality terms included in our data processing agreements. This prohibits such third parties from selling, trading, using, marketing or otherwise distributing GlobalSign customer data.
As Required by Law: We may also release your information when we believe release is appropriate to comply with the law or protect our rights, property, or safety.
It is our policy to notify customers of requests for their data from law enforcement unless we are prohibited from doing so by statute or court order. Law enforcement officials who believe that notification would jeopardize an investigation should obtain an appropriate court order or other process that specifically precludes member notification, such as an order issued pursuant to 18 U.S.C. §2705(b).
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The third parties, subsidiaries and affiliates to which your personal information can be disclosed may be located throughout the world. Therefore, information may be sent to countries having different privacy protection standards than your country of residence. In such cases, we take measures to ensure that your personal information receives an adequate level of protection, which includes the EU Standard Contractual Clauses to protect your personal information.
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The personal information we collect is retained for no longer than necessary to fulfil the stated purposes in section 2 above or for a period specifically required by law or regulation that GlobalSign is obligated to follow.
To meet public CA audit requirements as detailed in the GlobalSign Certification Practice Statement, personal data used to fulfill verification of certain types of digital certificate applications will be retained for a minimum of 10 years depending on the class of product or service and may be retained in either a physical or electronic format. Please refer to the GlobalSign Certification Practice Statement for full details.
After the retention period is over, GlobalSign securely disposes or anonymizes your personal information in order to prevent loss, theft, misuse, or unauthorized access.
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If at any time you would like to unsubscribe from receiving future emails, we include unsubscribe instructions at the bottom of each email.
Renewal notices may be cancelled on a per digital certificate basis by logging into your GlobalSign Certificate Center (GCC) account and disabling renewal notices.
Email preferences for CIT related/collected information can be updated and changed within CIT.
If GlobalSign is processing your personal data based on your consent, you may withdraw your consent at any time via the GlobalSign Preference Centre at https://downloads.globalsign.com/acton/media/2674/preference-center-login or by contacting us at one of the addresses shown in section 15 below.
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You are responsible for providing GlobalSign with true, accurate, current and complete personal information. Also, you are responsible to maintain and promptly update the information to keep it true, accurate, current and complete.
You have the right to access and modify your personal data stored on GlobalSign systems. You can exercise your rights by contacting us in writing. We will require you to provide identification in order to verify the authenticity as the data subject. We will make reasonable efforts to respond to and process your request as required by law.
To the extent of applicable law, you may have the right to request erasure of your personal information, restriction of processing as it applies to you, object to processing and the right to data portability. You may also have the right to lodge a complaint with a supervisory authority.
If you provide any information that is untrue, inaccurate, not current or incomplete, or if we have reasonable grounds to suspect that such information is untrue, inaccurate, not current or incomplete, we have the right to suspend or terminate your account and refuse any and all current or future services.
12. How we protect your information
We implement a variety of security measures to maintain the safety of your personal information when you place an order or enter, submit, or access your personal information. All supplied sensitive/credit information is transmitted via Secure Socket Layer (SSL).
After a transaction, your transaction-related information will be kept on file to meet audit requirements and facilitate renewals. We do not retain any credit card details.
13. Relevant laws
GlobalSign commits itself to protect the personal information submitted by applicants and subscribers for its public certification services. GlobalSign declares to fully respect all rights established and laid out in European Union and Member States' laws and regulations:
- - European Directive 95/46 on the protection of individuals with regard to the processing of personal data and on the free movement of such data and as replaced by Regulation EU 2016/679 on the protection of natural persons with regard to the processing of personal data and on the free movement of such data (the EU General Data Protection Regulation); and
- - Provisions of the GlobalSign CPS.
14. Changes to our Privacy Policy
If we make material changes to our privacy policy, we will inform customers by emailing a notice of the availability of a new version with a link to the new version.
15. Contact Us
If you have any inquires, or questions regarding our privacy policy, please contact us at:
- We use the data you submit only for purposes identified in section 3 of this privacy policy.
- You have the right to review your personal data that GlobalSign holds and check it for accuracy.
- You have the right to correct data in the case that errors may be found in our records.
- You have the right to request that any of your personal data be erased. i.e. right to be forgotten.
- You have the right to obtain and reuse use your personal data for your own purposes
- You have the right to request that GlobalSign restrict the processing of your personal data under certain circumstances.
- You have the right to object to our processing of your personal data.
14. Changes to our Privacy Policy
If we make material changes to our privacy policy, we will inform customers by emailing a notice of the availability of a new version with a link to the new version.
15. Contact Us
If you have any inquires, or questions regarding our privacy policy, please contact us at:
https://support.globalsign.com/
https://www.globalsign.com/en/company/contact/support/
https://jp.globalsign.com/support/
or
Deputy Data Protection Officer
GMO GlobalSign, Ltd.
Springfield House Sandling Road
Maidstone, Kent ME 14 2LP
United Kingdom
dpo@globalsign.com
16. Our Office Locations
GMO GlobalSign K.K., Tokyo, Japan
GMO GlobalSign Ltd., Maidstone, Kent, UK
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GMO GlobalSign, Inc., Portsmouth, NH, USA
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GMO GlobalSign Certificate Services Pvt. Ltd., Delhi, India
GlobalSign China Co., Ltd., Shanghai, China
GMO GlobalSign Inc., Manila, Philippines
GMO GlobalSign FZ-LLC, Dubai, UAEYou might enjoy:
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