Questions and Answers
What is the primary function of DNS resolution?
Which type of DNS record is used to map an alias or alternate name to a canonical name?
What is the purpose of a DNS resolver?
What is the term for injecting fake DNS records into a cache to redirect users to fake websites?
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What is the primary goal of DNSSEC?
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What is the purpose of a TTL in DNS caching?
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What type of DNS record is used to route email to a mail server?
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What is the main purpose of a PTR record in DNS?
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What is the term for the process of registering a domain name with a registrar?
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What is the primary function of DNS caching?
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What is the purpose of an SRV record in DNS?
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What is the effect of updating DNS records on cache entries?
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What determines how long DNS records remain in the cache?
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What is the main goal of the recursive DNS resolver in the DNS resolution process?
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What is stored in a WHOIS database?
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Which of the following is a security measure to mitigate DDoS attacks on DNS servers?
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What type of DNS record is used to specify the name servers responsible for a domain?
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What is the purpose of DNS over TLS (DoT) and DNS over HTTPS (DoH)?
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What is the first step in the DNS resolution process?
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What is the threat of cache poisoning in DNS?
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What is the purpose of a DNS resolver in a browser or OS?
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Study Notes
DNS Resolution
- The process of translating a domain name into an IP address
- Involves a series of requests between DNS servers to find the authoritative name server for a domain
- Steps:
- Browser or application sends a request to a DNS resolver (usually provided by the operating system or ISP)
- DNS resolver sends a request to a root DNS server
- Root DNS server responds with the address of a top-level domain (TLD) DNS server
- DNS resolver sends a request to the TLD DNS server
- TLD DNS server responds with the address of the authoritative name server for the domain
- DNS resolver sends a request to the authoritative name server
- Authoritative name server responds with the IP address associated with the domain name
DNS Record Types
- A records: map a domain name to an IP address
- NS records: identify the name servers responsible for a domain
- MX records: route email to a mail server
- CNAME records: map an alias or alternate name to a canonical name
- PTR records: map an IP address to a domain name (reverse DNS)
- TXT records: hold text information about a domain
- SOA records: specify the start of authority for a DNS zone
- SRV records: specify the location of services such as LDAP or SIP
DNS Security
- DNS spoofing: intercepting and altering DNS requests to redirect users to fake websites
- DNS cache poisoning: injecting fake DNS records into a DNS cache to redirect users to fake websites
- DNSSEC (Domain Name System Security Extensions): adds digital signatures to DNS records to ensure authenticity and integrity
- DNSSec validation: verifies the digital signatures of DNS records to ensure they come from the authoritative name server
DNS Caching
- DNS resolvers and DNS servers cache DNS records to improve performance and reduce latency
- Cache TTL (Time To Live): specifies how long a DNS record can be cached before it expires
- Cache poisoning: injecting fake DNS records into a cache to redirect users to fake websites
- DNS caching can be implemented at the browser, operating system, or ISP level
Domain Registration
- The process of registering a domain name with a registrar (e.g. GoDaddy, Namecheap)
- Domain registrars are accredited by ICANN (Internet Corporation for Assigned Names and Numbers)
- Registration information is stored in a WHOIS database
- Domain registration typically includes:
- Registrant contact information
- Administrative contact information
- Technical contact information
- Name servers for the domain
- Domain registration can be public or private (using WHOIS privacy services)
DNS Resolution
- DNS resolution is the process of translating a domain name into an IP address.
- It involves a series of requests between DNS servers to find the authoritative name server for a domain.
- The process starts with a browser or application sending a request to a DNS resolver.
- The DNS resolver sends requests to a root DNS server, then to a top-level domain (TLD) DNS server, and finally to the authoritative name server for the domain.
- The authoritative name server responds with the IP address associated with the domain name.
DNS Record Types
- A records map a domain name to an IP address.
- NS records identify the name servers responsible for a domain.
- MX records route email to a mail server.
- CNAME records map an alias or alternate name to a canonical name.
- PTR records map an IP address to a domain name (reverse DNS).
- TXT records hold text information about a domain.
- SOA records specify the start of authority for a DNS zone.
- SRV records specify the location of services such as LDAP or SIP.
DNS Security
- DNS spoofing is a type of attack where an attacker intercepts and alters DNS requests to redirect users to fake websites.
- DNS cache poisoning is a type of attack where an attacker injects fake DNS records into a DNS cache to redirect users to fake websites.
- DNSSEC (Domain Name System Security Extensions) adds digital signatures to DNS records to ensure authenticity and integrity.
- DNSSec validation verifies the digital signatures of DNS records to ensure they come from the authoritative name server.
DNS Caching
- DNS resolvers and DNS servers cache DNS records to improve performance and reduce latency.
- Cache TTL (Time To Live) specifies how long a DNS record can be cached before it expires.
- Cache poisoning is a type of attack where an attacker injects fake DNS records into a cache to redirect users to fake websites.
- DNS caching can be implemented at the browser, operating system, or ISP level.
Domain Registration
- Domain registration is the process of registering a domain name with a registrar (e.g. GoDaddy, Namecheap).
- Domain registrars are accredited by ICANN (Internet Corporation for Assigned Names and Numbers).
- Registration information is stored in a WHOIS database.
- Domain registration typically includes registrant contact information, administrative contact information, technical contact information, and name servers for the domain.
- Domain registration can be public or private (using WHOIS privacy services).
DNS Resolution
- DNS resolution is the process of translating a domain name into an IP address.
- It involves a series of requests between DNS servers to find the IP address associated with a domain name.
- The process includes:
- Recursive DNS resolver sending a query to a DNS recursive resolver.
- Recursive resolver querying a root DNS server to find the top-level domain (TLD) server associated with the domain.
- Recursive resolver querying the TLD server to find the authoritative DNS server for the domain.
- Authoritative DNS server returning the IP address associated with the domain.
- Recursive resolver returning the IP address to the original requester.
Domain Registration
- Domain registration is the process of registering a domain name with a domain name registrar.
- It requires choosing a domain name registrar, verifying domain ownership, providing contact information, and paying registration fees.
- Registration information is stored in a WHOIS database.
- Domain registration typically includes:
- Domain name.
- Registrant contact information.
- Name servers (DNS servers) responsible for the domain.
DNS Security
- Threats to DNS include:
- Cache poisoning (injecting false information into DNS caches).
- DNS spoofing (redirecting users to fake websites).
- DDoS attacks (overwhelming DNS servers with traffic).
- Security measures include:
- DNSSEC (Domain Name System Security Extensions) - adds digital signatures to DNS data to verify authenticity.
- DNS over TLS (DoT) and DNS over HTTPS (DoH) - encrypt DNS traffic.
- Rate limiting and IP blocking to mitigate DDoS attacks.
- Regularly updating DNS software and plugins to prevent vulnerabilities.
DNS Record Types
- Common DNS record types include:
- A record - maps a domain name to an IP address.
- NS record - specifies the name servers responsible for a domain.
- MX record - specifies the mail servers responsible for a domain.
- CNAME record - maps an alias or subdomain to a canonical domain name.
- PTR record - maps an IP address to a domain name (reverse DNS).
- TXT record - holds text information about a domain (e.g. SPF records).
- SRV record - specifies the location of services (e.g. LDAP or SIP).
DNS Caching
- DNS caching is the temporary storage of DNS query results to improve performance.
- Types of DNS caching include:
- Browser caching - stores DNS results in the browser's cache.
- Operating system caching - stores DNS results in the OS's cache.
- DNS resolver caching - stores DNS results in the DNS recursive resolver's cache.
- Authoritative DNS server caching - stores DNS results in the authoritative DNS server's cache.
- Cache expiration: DNS records have a time-to-live (TTL) that determines how long they remain in the cache.
- Cache invalidation: updating DNS records can invalidate cache entries, requiring a new DNS query.
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Description
Learn how domain names are translated into IP addresses through a series of requests between DNS servers.
