Amass is now an OWASP project and the OWASP GitHub organization repository is where all further development and releases will take place.

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.
Information Gathering Techniques Used:

• DNS: Basic enumeration, Brute forcing (upon request), Reverse DNS sweeping, Subdomain name alterations/permutations, Zone transfers (upon request)
  
• Scraping: Ask, Baidu, Bing, CommonCrawl, DNSDumpster, DNSTable, Dogpile, Exalead, Google, HackerOne, IPv4Info, Netcraft, PTRArchive, Riddler, SiteDossier, ViewDNS, Yahoo
  
• Certificates: Active pulls (upon request), Censys, CertSpotter, Crtsh, Entrust
  
• APIs: AlienVault, BinaryEdge, BufferOver, CIRCL, DNSDB, HackerTarget, Mnemonic, NetworksDB, PassiveTotal, RADb, Robtex, SecurityTrails, ShadowServer, Shodan, Spyse (CertDB & FindSubdomains), Sublist3rAPI, TeamCymru, ThreatCrowd, Twitter, Umbrella, URLScan, VirusTotal
  
• Web Archives: ArchiveIt, ArchiveToday, Arquivo, LoCArchive, OpenUKArchive, UKGovArchive, Wayback