Reverse DNS Lookup
This tool will provide you the hostname (ie www.yahoo.com) of the IP address that you enter below.
Results:
Lookup on IPv4 Address: 161.148.231.101
Hostname: srfweb01.receita.fazenda.gov.br
Hostname: e-receita.receita.fazenda.gov.br
Hostname: www2.receita.fazenda.gov.br