diff --git a/CHANGELOG b/CHANGELOG
index 388e34a48..61fb69aa9 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE] Added the script duplicates which attempts to determine duplicate
+  hosts by analyzing information collected by other scripts. [Patrik Karlsson]
+
 Nmap 5.61TEST5 [2012-03-09]
 
 o Integrated all of your IPv4 OS fingerprint submissions since June
diff --git a/scripts/duplicates.nse b/scripts/duplicates.nse
new file mode 100644
index 000000000..a6340e7dc
--- /dev/null
+++ b/scripts/duplicates.nse
@@ -0,0 +1,261 @@
+description = [[
+The duplicates script attempts to discover multihomed systems by analysing and
+comparing information collected by other scripts. The information analyzed
+currently includes:
+  - SSL Certificates
+  - SSH Host keys
+  - MAC Address
+  - Netbios Server Name
+
+In order for the script to be able to analyze the data it has dependencies to
+the following scripts: ssl-cert,ssh-hostkey,nbtstat.
+
+One or more of these scripts have to be run in order to allow the duplicates
+script to analyze the data.
+]]
+
+---
+-- @usage
+-- sudo nmap -PN -p445,443 --script duplicates,nbstat,ssl-cert <ips>
+--
+-- @output
+-- | duplicates: 
+-- |   ARP
+-- |       MAC: 01:23:45:67:89:0a
+-- |           192.168.99.10
+-- |           192.168.99.11
+-- |   Netbios
+-- |       Server Name: WIN2KSRV001
+-- |           192.168.0.10
+-- |_          192.168.1.10
+--
+
+
+--
+-- While the script provides basic duplicate functionality, here are some ideas
+-- on improvements.
+--
+-- Possible additional information sources:
+-- * Microsoft SQL Server instance names (Match hostname, version, instance
+--   names and ports) - Reliable given several instances
+-- * Oracle TNS names - Not very reliable
+--
+-- Possible enhancements:
+-- * Compare hosts across information sources and create a global category
+--   in which system duplicates are reported based on more than one source.
+-- * Add a reliability index for each information source that indicates how
+--   reliable the duplicate match was. This could be an index compared to
+--   other information sources as well as an indicator of how good the match
+--   was for a particular information source.
+
+author = "Patrik Karlsson"
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+categories = {"safe"}
+dependencies = {"ssl-cert", "ssh-hostkey", "nbstat"}
+
+require 'ipOps'
+
+hostrule = function() return true end
+postrule = function() return true end
+
+--- check for the presence of a value in a table
+--@param tab the table to search into
+--@param item the searched value
+--@return a boolean indicating whether the value has been found or not
+local function contains(tab, item)
+	for _, val in pairs(tab) do
+		if val == item then
+			return true
+		end
+	end
+	return false
+end
+
+local function processSSLCerts(tab)
+	
+	-- Handle SSL-certificates
+	-- We create a new table using the SHA1 digest as index
+	local ssl_certs = {}
+	for host, v in pairs(tab) do
+		for port, sha1 in pairs(v) do
+			ssl_certs[sha1] = ssl_certs[sha1] or {}
+			if ( not contains(ssl_certs[sha1], host.ip) ) then
+				table.insert(ssl_certs[sha1], host.ip)
+			end
+		end
+	end
+	
+	local results = {}
+	for sha1, hosts in pairs(ssl_certs) do
+		table.sort(hosts, function(a, b) return ipOps.compare_ip(a, "lt", b) end)
+		if ( #hosts > 1 ) then
+			table.insert(results, { name = ("Certficate (%s)"):format(sha1), hosts } )
+		end
+	end
+	
+	return results
+end
+
+local function processSSHKeys(tab)
+
+	local hostkeys = {}
+
+	-- create a reverse mapping key_fingerprint -> host(s)
+	for ip, keys in pairs(tab) do
+		for _, key in ipairs(keys) do
+			local fp = ssh1.fingerprint_hex(key.fingerprint, key.algorithm, key.bits)
+			if not hostkeys[fp] then
+				hostkeys[fp] = {}
+			end
+			-- discard duplicate IPs
+			if not contains(hostkeys[fp], ip) then
+				table.insert(hostkeys[fp], ip)
+			end
+		end
+	end
+
+	-- look for hosts using the same hostkey
+	local results = {}
+	for key, hosts in pairs(hostkeys) do
+		if #hostkeys[key] > 1 then
+			table.sort(hostkeys[key], function(a, b) return ipOps.compare_ip(a, "lt", b) end)
+			local str = 'Key ' .. key .. ':'
+			table.insert( results, { name = str, hostkeys[key] } )
+		end
+	end
+
+	return results
+end
+
+local function processNBStat(tab)
+
+	local results, mac_table, name_table = {}, {}, {}
+	for host, v in pairs(tab) do
+		mac_table[v.mac] = mac_table[v.mac] or {}
+		if ( not(contains(mac_table[v.mac], host.ip)) ) then
+			table.insert(mac_table[v.mac], host.ip)
+		end
+
+		name_table[v.server_name] = name_table[v.server_name] or {}
+		if ( not(contains(name_table[v.server_name], host.ip)) ) then
+			table.insert(name_table[v.server_name], host.ip)
+		end
+	end
+	
+	for mac, hosts in pairs(mac_table) do
+		if ( #hosts > 1 ) then
+			table.sort(hosts, function(a, b) return ipOps.compare_ip(a, "lt", b) end)
+			table.insert(results, { name = ("MAC: %s"):format(mac), hosts })
+		end
+	end
+	
+	for srvname, hosts in pairs(name_table) do
+		if ( #hosts > 1 ) then
+			table.sort(hosts, function(a, b) return ipOps.compare_ip(a, "lt", b) end)
+			table.insert(results, { name = ("Server Name: %s"):format(srvname), hosts })
+		end
+	end
+	
+	return results
+end
+
+local function processMAC(tab)
+	
+	local function format_mac(mac)
+		local octets = {}
+		for _, v in ipairs({ string.byte(mac, 1, #mac) }) do
+			octets[#octets + 1] = string.format("%02x", v)
+		end
+		return stdnse.strjoin(":", octets)
+	end
+	
+	local mac
+	local mac_table = {}
+	
+	for host in pairs(tab) do
+		if ( host.mac_addr ) then
+			mac = format_mac(host.mac_addr)
+			mac_table[mac] = mac_table[mac] or {}
+			if ( not(contains(mac_table[mac], host.ip)) ) then
+				table.insert(mac_table[mac], host.ip)
+			end
+		end
+	end
+	
+	local results = {}
+	for mac, hosts in pairs(mac_table) do
+		if ( #hosts > 1 ) then
+			table.sort(hosts, function(a, b) return ipOps.compare_ip(a, "lt", b) end)
+			table.insert(results, { name = ("MAC: %s"):format(mac), hosts })
+		end
+	end
+	
+	return results
+end
+
+postaction = function()
+	
+	local handlers = {
+		['ssl-cert'] = { func = processSSLCerts, name = "SSL" },
+		['sshhostkey'] = { func = processSSHKeys, name = "SSH" },
+		['nbstat'] = { func = processNBStat, name = "Netbios" },
+		['mac'] = { func = processMAC, name = "ARP" }
+	}
+	
+	-- temporary re-allocation code for SSH keys
+	for k, v in pairs(nmap.registry.sshhostkey or {}) do
+		nmap.registry['duplicates'] = nmap.registry['duplicates'] or {}
+		nmap.registry['duplicates']['sshhostkey'] = nmap.registry['duplicates']['sshhostkey'] or {}
+		nmap.registry['duplicates']['sshhostkey'][k] = v
+	end
+	
+	if ( not(nmap.registry['duplicates']) ) then
+		return
+	end
+	
+	local results = {}
+	for key, handler in pairs(handlers) do
+		if ( nmap.registry['duplicates'][key] ) then
+			local result_part = handler.func( nmap.registry['duplicates'][key] )
+			if ( result_part and #result_part > 0 ) then
+				table.insert(results, { name = handler.name, result_part } )
+			end
+		end
+	end
+	
+	return stdnse.format_output(true, results)
+end
+
+-- we have no real action in here. In essence we move information from the
+-- host based registry to the global one, so that our postrule has access to
+-- it when we need it.
+hostaction = function(host)
+
+	nmap.registry['duplicates'] = nmap.registry['duplicates'] or {}
+
+	for port, cert in pairs(host.registry["ssl-cert"] or {}) do
+		nmap.registry['duplicates']['ssl-cert'] = nmap.registry['duplicates']['ssl-cert'] or {}
+		nmap.registry['duplicates']['ssl-cert'][host] = nmap.registry['duplicates']['ssl-cert'][host] or {}
+		nmap.registry['duplicates']['ssl-cert'][host][port] = stdnse.tohex(cert:digest("sha1"), { separator = " ", group = 4 })
+	end
+	
+	if ( host.registry['nbstat'] ) then
+		nmap.registry['duplicates']['nbstat'] = nmap.registry['duplicates']['nbstat'] or {}
+		nmap.registry['duplicates']['nbstat'][host] = host.registry['nbstat']
+	end
+
+	if ( host.mac_addr_src ) then
+		nmap.registry['duplicates']['mac'] = nmap.registry['duplicates']['mac'] or {}
+		nmap.registry['duplicates']['mac'][host] = true
+	end
+
+	return
+end
+
+local Actions = {
+  hostrule = hostaction,
+  postrule = postaction
+}
+
+-- execute the action function corresponding to the current rule
+action = function(...) return Actions[SCRIPT_TYPE](...) end
diff --git a/scripts/nbstat.nse b/scripts/nbstat.nse
index e4d07330f..61ecf015f 100644
--- a/scripts/nbstat.nse
+++ b/scripts/nbstat.nse
@@ -110,6 +110,10 @@ action = function(host)
 		if manuf == nil then
 			manuf = "unknown"
 		end
+		host.registry['nbstat'] = { 
+			server_name = server_name, 
+			mac = ("%02x:%02x:%02x:%02x:%02x:%02x"):format( statistics:byte(1), statistics:byte(2), statistics:byte(3), statistics:byte(4), statistics:byte(5), statistics:byte(6) )
+		}
 		mac = string.format("%02x:%02x:%02x:%02x:%02x:%02x (%s)", statistics:byte(1), statistics:byte(2), statistics:byte(3), statistics:byte(4), statistics:byte(5), statistics:byte(6), manuf)
 		-- Samba doesn't set the Mac address, and nmap-mac-prefixes shows that as Xerox
 		if(mac == "00:00:00:00:00:00 (Xerox)") then
diff --git a/scripts/script.db b/scripts/script.db
index 652863dde..1ac3cf8ca 100644
--- a/scripts/script.db
+++ b/scripts/script.db
@@ -78,6 +78,7 @@ Entry { filename = "domino-enum-users.nse", categories = { "auth", "intrusive",
 Entry { filename = "dpap-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "drda-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "drda-info.nse", categories = { "discovery", "safe", "version", } }
+Entry { filename = "duplicates.nse", categories = { "safe", } }
 Entry { filename = "eap-info.nse", categories = { "broadcast", "safe", } }
 Entry { filename = "epmd-info.nse", categories = { "default", "discovery", "safe", } }
 Entry { filename = "finger.nse", categories = { "default", "discovery", "safe", } }