Это сработало для меня:
function AuthenticateUser(Username,Password,Domain)
dim strUser,strPass,strQuery,oConn,cmd,oRS
AuthenticateUser = false
strQuery = "SELECT cn FROM 'LDAP://" & Domain & "' WHERE objectClass='*'"
set oConn = server.CreateObject("ADODB.Connection")
oConn.Provider = "ADsDSOOBJECT"
oConn.properties("User ID") = Username
oConn.properties("Password")=Password
oConn.properties("Encrypt Password") = true
oConn.open "DS Query", Username,Password
set cmd = server.CreateObject("ADODB.Command")
set cmd.ActiveConnection = oConn
cmd.CommandText = strQuery
on error resume next
set oRS = cmd.Execute
if oRS.bof or oRS.eof then
AuthenticateUser = false
else
AuthenticateUser = true
end if
set oRS = nothing
set oConn = nothing
end function