DNS Flashcards
Why should you never run an authoritative and recursive server on the same system
Running authoritative and recursive DNS on the same system is insecure because recursive servers handle user queries and can have their cache poisoned, spreading malicious data. Combining it with authoritative functions risks exposing sensitive data about internal networks and enables attackers to exploit the system for amplification attacks. Separation isolates these roles, reducing vulnerabilities and maintaining security.
What is the main role of DNS
DNS maps domain names to IP addresses and IP addresses to domain names
Why is DNS difficult to secure
- DNS lacks built-in security, making it vulnerable to attacks like spoofing.
- Its global infrastructure is highly complex and difficult to secure consistently.
- Political and administrative control adds challenges to improving DNS security.
What is DNS caching and why is it important
DNS caching stores query results temporarily to reduce lookup times and improve performance
What is cache poisoning in DNS
It misleads DNS queries to redirect users to malicious websites
Why are certificates important in DNS
Certificates are important in DNS because they prevent attacks like DNS cache poisoning and spoofing by verifying the authenticity of DNS responses. They ensure that the data comes from a trusted source, protecting users from being redirected to malicious websites.
What is the maximum size for DNS names
255 bytes with 63 bytes per label
What is a DNS zone
It is a group of resource records served from one primary nameserver
What are A and AAAA records in DNS
A records map to IPv4 addresses while AAAA records map to IPv6 addresses
What does TTL stand for in DNS
Time to Live which defines how long a record can be cached
What is the Kaminsky Attack
A DNS vulnerability exploiting predictable transaction IDs to poison caches.
Process;
The Kaminsky Attack works by guessing predictable DNS transaction IDs to send fake responses, which the resolver accepts and caches, redirecting users to malicious sites.
What are recursive servers in DNS
Recursive servers in DNS resolve user queries by contacting other DNS servers as needed to find the complete answer.
What are authoritative servers in DNS
Authoritative DNS servers store and provide definitive answers for specific DNS zones they are configured to manage, delivering accurate resource record data without needing to query other servers.
What are glue records in DNS
They are A(IPv4) or AAAA(IPv6) records for nameservers to prevent resolution loops
What is the function of a DNS resolver
A DNS resolver is a client that queries the DNS system to translate domain names into IP addresses and processes the responses to return the requested information.
What is EDNS0 in DNS
An extension mechanism for DNS with support for larger payloads and cookies
What is DNS over HTTPS (DoH)
DNS over HTTPS (DoH) encrypts DNS queries using HTTPS to enhance privacy and prevent third parties from intercepting or modifying DNS traffic
Why is DoH controversial
DoH is controversial because it bypasses traditional DNS controls, such as those used by network administrators for filtering and monitoring, making it harder to enforce policies or detect malicious activity. This can lead to challenges in network management and security.
What are Response Policy Zones RPZ in DNS
RPZs are used to block, redirect, or filter DNS responses based on security policies.
What is reverse mapping in DNS
It resolves IP addresses back to domain names using in-addr.arpa or ip6.arpa
Why are primary and secondary nameservers used in DNS
They are used for redundancy, load balancing, and reliability, ensuring DNS queries are resolved even if the primary nameserver fails
What is a zone file in DNS
A zone file is a text file that contains DNS records for a domain, including A, CNAME, MX, NS, and SOA records, to define mappings and settings for the DNS zone.
What is label compression in DNS
It reduces message size by reusing labels in DNS packets
Label = parts of domain name i.e. www or google or com
What is the role of mail exchangers MX in DNS
They define mail servers for a domain
