DNS
DNS is mostly UDP/53, but DNS will rely on TCP/53 more heavily as time progresses. DNS has always been designed to use both UDP and TCP port 53 from the start, with UDP being the default, and falls back to using TCP when it cannot communicate on UDP, typically when the packet size is too large to push through in a single UDP packet.
Also treated in DNS
Enumeration
DNS Zone Transfer
Tools like Fierce can also be used to enumerate all DNS servers of the root domain and scan for a DNS zone transfer:
Domain Takeovers & Subdomain Enumeration
Subdomain Enumeration
An excellent alternative is a tool called Subbrute. This tool allows us to use self-defined resolvers and perform pure DNS brute-forcing attacks during internal penetration tests on hosts that do not have Internet access.
The tool has found four subdomains associated with inlanefreight.com. Using the nslookup or host command, we can enumerate the CNAME records for those subdomains.
The support subdomain has an alias record pointing to an AWS S3 bucket. However, the URL https://support.inlanefreight.com shows a NoSuchBucket error indicating that the subdomain is potentially vulnerable to a subdomain takeover. Now, we can take over the subdomain by creating an AWS S3 bucket with the same subdomain name.
The can-i-take-over-xyz repository is also an excellent reference for a subdomain takeover vulnerability.
DNS Spoofing
Example attack paths for the DNS Cache Poisoning are as follows:
An attacker could intercept the communication between a user and a DNS server to route the user to a fraudulent destination instead of a legitimate one by performing a Man-in-the-Middle (
MITM) attack.Exploiting a vulnerability found in a DNS server could yield control over the server by an attacker to modify the DNS records.
Local DNS Cache Poisoning
From a local network perspective, an attacker can also perform DNS Cache Poisoning using MITM tools like Ettercap or Bettercap.
To exploit the DNS cache poisoning via Ettercap, we should first edit the /etc/ettercap/etter.dns file to map the target domain name (e.g., inlanefreight.com) that they want to spoof and the attacker's IP address (e.g., 192.168.225.110) that they want to redirect a user to:
Next, start the Ettercap tool and scan for live hosts within the network by navigating to Hosts > Scan for Hosts. Once completed, add the target IP address (e.g., 192.168.152.129) to Target1 and add a default gateway IP (e.g., 192.168.152.2) to Target2.
Activate dns_spoof attack by navigating to Plugins > Manage Plugins. This sends the target machine with fake DNS responses that will resolve inlanefreight.com to IP address 192.168.225.110
After a successful DNS spoof attack, if a victim user coming from the target machine 192.168.152.129 visits the inlanefreight.com domain on a web browser, they will be redirected to a Fake page that is hosted on IP address 192.168.225.110:
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