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A subdomain takeover is a security flaw that happens when an entity that controls the parent domain (example.com) no longer uses a subdomain (for example, subdomain.example.com), but the DNS records for that subdomain still refer to an operational server or service. As a result, the subdomain can be hijacked by an attacker who can then register it and take over the server or service. Once an attacker obtains control of a subdomain, they can utilize it for a variety of harmful tasks like malware distribution, phishing, and content spoofing. In rare circumstances, the attacker might even be able to access confidential data or launch assaults that escalate their privileges on the parent domain.
There are several methods to find subdomain takeovers in 2023. Some popular methods include:
- Manual Recon: This involves manually reviewing a target’s website and subdomains for potential vulnerabilities, such as misconfigured DNS records or unclaimed cloud services.
- Automated Tools: There are various automated tools available, such as Sublist3r, Amass, and Knockpy, that can help you identify subdomains and potential takeover vulnerabilities.
- Search Engines: You can also use search engines like Google, Bing, and Yahoo to search for subdomains by using advanced search operators, such as “site:domain.com” or “inurl:domain.com”
- Public Data Breaches: Many subdomains are leaked in data breaches, so looking through public data breaches and checking if any of the subdomains match with the target.
- Bug Bounty Platforms: Some companies have bug bounty programs where you can report subdomain takeover vulnerabilities.
- Social Media: You can also check social media platforms like Twitter, LinkedIn, and GitHub for information about a target’s subdomains.
Prevention for Subdomain Takeover
Organizations should periodically check and update their DNS records, make sure all cloud-based services and domains are appropriately secured, and review and update their DNS records to prevent subdomain takeover. They should also establish a procedure for swiftly identifying and resolving potential subdomain takeover issues. They should also routinely check for any unauthorized modifications to their DNS records.
Furthermore, businesses ought to think about adopting a bug bounty program, which incentivizes security experts to report vulnerabilities in return for a payout. This can be a useful technique for locating and fixing subdomain takeover problems before attackers can use them.
It is crucial to keep in mind that locating and avoiding subdomain takeover vulnerabilities can be challenging and time-consuming, and it may even call for knowledge of diverse technical capabilities. Prior to attempting to exploit any vulnerabilities, it’s crucial to follow the responsible disclosure policy and receive approval from the targeted organization. For more details, you may refer to: https://github.com/EdOverflow/can-i-take-over-xyz and https://x64.coffee/2022/03/10/dangling-dns.html