TCP 25 Replication SMTP TCP/UDP 53 User and Computer Authentication, Name Resolution, Trusts DNS TCP/UDP 88 User and Computer Authentication, Forest Level Trusts Kerberos UDP 123 Windows Time, Trusts Windows Time, NTP, SNTP TCP 135 Replication RPC, EPM UDP 137 User and Computer Authentication, NetLogon, NetBIOS Name Resolution UDP 138 DFS, Group Policy DFSN, NetLogon, NetBIOS Datagram Service TCP 139 User and Computer Authentication, Replication DFSN, NetBIOS Session Service, Net TCP/UDP 389 Directory, Replication, User and Computer Authentication, Group Policy, Trusts LDAP TCP/UDP 445 Replication, User and Computer Authentication, Group Policy, Trusts SMB,CIFS,SMB2, DFSN, LSARPC, NbtSS, NetLogonR, SamR, SrvSvc Sense of Security - 2018 Active Directory Common Ports Used 15 August 18