The Network programs discussed over here are:
NETSTAT.exe (TCP/IP Net Connections)
PING.exe
TRACERT.exe (Trace Route)
NBSTAT.exe
ROUTE.exe
ARP.exe
NETSTAT.exe TCP/IP Network Statistics
Displays protocol statistics and current TCP/IP network connections.
NETSTAT [-a] [-e] [-n] [-s] [-p proto] [-r] [interval]
-a Displays all connections and listening ports.
-e Displays Ethernet statistics. This may be combined with the
-s option.
-n Displays addresses and port numbers in numerical form.
-p proto Shows connections for the protocol specified by proto; proto
may be TCP or UDP. If used with the -s option to display
per-protocol statistics, proto may be TCP, UDP, or IP.
-r Displays the routing table.
-s Displays per-protocol statistics. By default, statistics
are shown for TCP, UDP and IP; the -p option may be used
to specify a subset of the default.
interval Redisplays selected statistics, pausing interval seconds
between each display. Press CTRL+C to stop redisplaying
statistics. If omitted, netstat will print the current
configuration information once.
First, I would recommend that you always use the '-a' parameter so you can see UDP 'listening ports' as well (often used by trojans), and not just the active TCP connections; then switch between using the '-a' and no parameters at all, to see the differences. When you're offline, you normally shouldn't see any connection data! If you do see an OPEN PORT NUMBER 'listening' for a connection (using the '-a' parameter), it may be that your computer has been infected with a trojan! Click this link for a few more ideas on how you can check to see if your computer is Trojan Free?
If you're running a server, such as the free XITAMI server, you might see something like this ("My_Comp" is the name of my computer):
C:\WINDOWS>netstat -a
Active Connections
Proto Local Address Foreign Address State
TCP My_Comp:ftp localhost:0 LISTENING
TCP My_Comp:80 localhost:0 LISTENING
Or with the "-an" parameters:
C:\WINDOWS>netstat -an
By simply opening a browser connection to both the HTTP (port 80) and FTP (port 21) servers (while still offline!), I saw the following:
C:\WINDOWS>netstat -a
Active Connections
Proto Local Address Foreign Address State
TCP My_Comp:ftp localhost:0 LISTENING
TCP My_Comp:80 localhost:0 LISTENING
TCP My_Comp:1104 localhost:0 LISTENING
TCP My_Comp:ftp localhost:1104 ESTABLISHED
TCP My_Comp:1102 localhost:0 LISTENING
TCP My_Comp:1103 localhost:0 LISTENING
TCP My_Comp:80 localhost:1111 TIME_WAIT
TCP My_Comp:1104 localhost:ftp ESTABLISHED
TCP My_Comp:1107 localhost:0 LISTENING
PING.exe
Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
[-r count] [-s count] [[-j host-list] | [-k host-list]]
[-w timeout] destination-list
Options:
-t Ping the specifed host until interrupted.
-a Resolve addresses to hostnames.
-n count Number of echo requests to send.
-l size Send buffer size.
-f Set "Don't Fragment" flag in packet.
-i TTL Time To Live.
-v TOS Type Of Service.
-r count Record route for count hops.
-s count Timestamp for count hops.
-j host-list Loose source route along host-list.
-k host-list Strict source route along host-list.
-w timeout Timeout in milliseconds to wait for each reply.
There's one special IP number everyone should know about:
127.0.0.1 - localhost (or loopback).
This is used to connect ( through a browser, for example) to a Web server on your own computer. (127 being reserved for this purpose.) You can use this IP number at all times. It doesn't matter if you're connected to the Internet or not.
It's also called the loopback address because you can ping it and get returns even when you're offline (not connected to any network). If you don't get any valid replies, then there's a problem with the computer's Network settings. Here's a typical response to the 'ping' command:(Attachment)
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