OWASP Amass is described as 'The OWASP Amass Project has developed a tool to help information security professionals perform network mapping of attack surfaces and perform external asset discovery using open source information gathering and active reconnaissance techniques' and is an app. There are eight alternatives to OWASP Amass for a variety of platforms, including Linux, Web-based, Self-Hosted, SaaS and BSD apps. The best OWASP Amass alternative is sn0int, which is both free and Open Source. Other great apps like OWASP Amass are BitNinja Server Security, Subfinder, Dnscan and Sublist3r.