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Fix refguide indexterms mucking with manpage again. Fixes #463 [ci skip]
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docs/nmap.1
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docs/nmap.1
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.\" Title: nmap
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.\" Author: [see the "Author" section]
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.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
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.\" Date: 07/19/2016
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.\" Date: 07/22/2016
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.\" Manual: Nmap Reference Guide
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.\" Source: Nmap
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.\" Language: English
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.\"
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.TH "NMAP" "1" "07/19/2016" "Nmap" "Nmap Reference Guide"
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.TH "NMAP" "1" "07/22/2016" "Nmap" "Nmap Reference Guide"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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@@ -729,32 +729,38 @@ filtered\&.
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.PP
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\fBThe six port states recognized by Nmap\fR
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.PP
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.\" open port state open
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open
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.\" open port state
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.RS 4
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An application is actively accepting TCP connections, UDP datagrams or SCTP associations on this port\&. Finding these is often the primary goal of port scanning\&. Security\-minded people know that each open port is an avenue for attack\&. Attackers and pen\-testers want to exploit the open ports, while administrators try to close or protect them with firewalls without thwarting legitimate users\&. Open ports are also interesting for non\-security scans because they show services available for use on the network\&.
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.RE
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.PP
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.\" closed port state closed
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closed
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.\" closed port state
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.RS 4
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A closed port is accessible (it receives and responds to Nmap probe packets), but there is no application listening on it\&. They can be helpful in showing that a host is up on an IP address (host discovery, or ping scanning), and as part of OS detection\&. Because closed ports are reachable, it may be worth scanning later in case some open up\&. Administrators may want to consider blocking such ports with a firewall\&. Then they would appear in the filtered state, discussed next\&.
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.RE
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.PP
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.\" filtered port state filtered
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filtered
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.\" filtered port state
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.RS 4
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Nmap cannot determine whether the port is open because packet filtering prevents its probes from reaching the port\&. The filtering could be from a dedicated firewall device, router rules, or host\-based firewall software\&. These ports frustrate attackers because they provide so little information\&. Sometimes they respond with ICMP error messages such as type 3 code 13 (destination unreachable: communication administratively prohibited), but filters that simply drop probes without responding are far more common\&. This forces Nmap to retry several times just in case the probe was dropped due to network congestion rather than filtering\&. This slows down the scan dramatically\&.
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.RE
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.PP
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.\" unfiltered port state unfiltered
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unfiltered
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.\" unfiltered port state
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.RS 4
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The unfiltered state means that a port is accessible, but Nmap is unable to determine whether it is open or closed\&. Only the ACK scan, which is used to map firewall rulesets, classifies ports into this state\&. Scanning unfiltered ports with other scan types such as Window scan, SYN scan, or FIN scan, may help resolve whether the port is open\&.
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.RE
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.PP
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.\" open|filtered port state open|filtered
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open|filtered
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.\" open|filtered port state
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.RS 4
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Nmap places ports in this state when it is unable to determine whether a port is open or filtered\&. This occurs for scan types in which open ports give no response\&. The lack of response could also mean that a packet filter dropped the probe or any response it elicited\&. So Nmap does not know for sure whether the port is open or being filtered\&. The UDP, IP protocol, FIN, NULL, and Xmas scans classify ports this way\&.
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.RE
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.PP
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.\" closed|filtered port state closed|filtered
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closed|filtered
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.\" closed|filtered port state
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.RS 4
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This state is used when Nmap is unable to determine whether a port is closed or filtered\&. It is only used for the IP ID idle scan\&.
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.RE
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@@ -1031,9 +1031,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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<variablelist><title>The six port states recognized by Nmap</title>
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<varlistentry><term>
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<varlistentry><term>open
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<indexterm><primary><literal>open</literal> port state</primary></indexterm>
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open</term>
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</term>
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<listitem><para>An application is actively accepting TCP
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connections, UDP datagrams or SCTP associations on this port.
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Finding these is often the primary goal of port scanning.
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@@ -1045,9 +1045,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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services available for use on the network.
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</para></listitem></varlistentry>
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<varlistentry><term>
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<varlistentry><term>closed
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<indexterm><primary><literal>closed</literal> port state</primary></indexterm>
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closed</term>
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</term>
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<listitem><para>A closed port is accessible (it receives and
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responds to Nmap probe packets), but there is no application
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@@ -1059,9 +1059,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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appear in the filtered state, discussed next.
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</para></listitem></varlistentry>
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<varlistentry><term>
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<varlistentry><term>filtered
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<indexterm><primary><literal>filtered</literal> port state</primary></indexterm>
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filtered</term>
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</term>
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<listitem><para>Nmap cannot determine whether the port is open
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because packet filtering prevents its probes from reaching the port.
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@@ -1075,9 +1075,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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in case the probe was dropped due to network congestion rather than
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filtering. This slows down the scan dramatically.</para></listitem></varlistentry>
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<varlistentry><term>
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<varlistentry><term>unfiltered
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<indexterm><primary><literal>unfiltered</literal> port state</primary></indexterm>
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unfiltered</term>
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</term>
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<listitem><para>The unfiltered state means that a port is accessible,
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but Nmap is unable to determine whether it is open or closed. Only
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the ACK scan, which is used to map firewall rulesets, classifies
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@@ -1086,9 +1086,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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whether the port is open.
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</para></listitem></varlistentry>
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<varlistentry><term>
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<varlistentry><term>open|filtered
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<indexterm><primary><literal>open|filtered</literal> port state</primary></indexterm>
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open|filtered</term>
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</term>
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<listitem><para>Nmap places ports in this state when it is unable to
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determine whether a port is open or filtered. This occurs for scan
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types in which open ports give no response. The lack of
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@@ -1098,9 +1098,9 @@ options from across the Internet might show that port as <literal>filtered</lite
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FIN, NULL, and Xmas scans classify ports this
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way.</para></listitem></varlistentry>
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<varlistentry><term>
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<varlistentry><term>closed|filtered
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<indexterm><primary><literal>closed|filtered</literal> port state</primary></indexterm>
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closed|filtered</term>
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</term>
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<listitem><para>This state is used when Nmap is unable to determine
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whether a port is closed or filtered. It is only used for the IP ID
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idle scan.</para></listitem></varlistentry>
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