Sublist3r is a Python-based tool that can be utilized during domain harvesting, which can enumerate sub-domains of a primary domain using OSINT. The tool utilizes APIs such as Google, Bing, Baidu, and ASK search engines. It also searches in NetCraft, Virustotal, ThreatCrowd, DNSdumpster, and reverseDNS; this also performs brute force using a specific wordlist.

The tool can be directly downloaded from GitHub, or by running git clone https://github.com/aboul3la/Sublist3r/ in the Kali Terminal.

Once the tool is downloaded, ensure you install the requirements and then run the tool to harvest the sub-domains of your target, as shown in the following screenshot: